[Federal Register Volume 88, Number 46 (Thursday, March 9, 2023)]
[Proposed Rules]
[Pages 14536-14560]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-04680]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R8-ES-2022-0165; FF09E21000 FXES1111090FEDR 234]


Endangered and Threatened Wildlife and Plants; Petition Finding 
for Joshua Trees (Yucca brevifolia and Y. jaegeriana)

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notification of finding.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 
12-month finding on a petition to list Joshua trees (Yucca brevifolia 
and Y. jaegeriana) as endangered or threatened species under the 
Endangered Species Act of 1973, as amended (Act). After a thorough 
review of the best available scientific and commercial information, we 
find that listing Joshua trees as endangered or threatened species is 
not warranted. However, we ask the public to submit to us any new 
information that becomes available concerning the threats to the Joshua 
trees or their habitat at any time.

DATES: The finding in this document was made on March 9, 2023.

ADDRESSES: This finding is available on the internet at https://www.regulations.gov under Docket No. FWS-R8-ES-2022-0165. Supporting 
information that we developed for this finding, including the species 
assessment form, species status assessment report, and peer review, are 
available at https://www.regulations.gov under Docket No. FWS-R8-ES-
2022-0165 and on the Service's website at https://www.fws.gov/office/carlsbad-fish-and-wildlife/library. Supporting information is also 
available for public inspection, by appointment, during normal business 
hours at the U.S. Fish and Wildlife Service, Carlsbad Ecological 
Services Field Office, 2177 Salk Avenue, Suite 250, Carlsbad, CA 92008. 
Please submit any new information, materials, comments, or questions 
concerning this finding to the person listed under FOR FURTHER 
INFORMATION CONTACT.

FOR FURTHER INFORMATION CONTACT: Scott Sobiech, Field Supervisor, U.S. 
Fish and Wildlife Service, Carlsbad Ecological Services Field Office, 
2177 Salk Avenue, Suite 250, Carlsbad, CA 92008; telephone 760-431-
9440. Individuals in the United States who are deaf, deafblind, hard of 
hearing, or have a speech disability may dial 711 (TTY, TDD, or 
TeleBraille) to access telecommunications relay services. Individuals 
outside the United States should use the relay services offered within 
their country to make international calls to the point-of-contact in 
the United States.

SUPPLEMENTARY INFORMATION: 

Previous Federal Actions

    On September 29, 2015, we received a petition from Taylor Jones 
(representing WildEarth Guardians), requesting that Yucca brevifolia--
either as a full species (Y. brevifolia) or as two subspecies (Y. b. 
brevifolia and Y. b. jaegeriana)--be listed as threatened and, if 
applicable, critical habitat be designated. On September 14, 2016, we 
published a 90-day finding in the Federal Register (81 FR 63160) 
concluding that the petition presented substantial information 
indicating that listing the Joshua tree may be warranted. On August 15, 
2019, we published a 12-month finding (84 FR 41694) concluding that 
listing either Y. brevifolia or Y. jaegeriana was not warranted. On 
November 4, 2019, WildEarth Guardians filed a complaint in the Central 
District of California challenging the analyses and listing decisions. 
The court vacated and remanded the listing decisions back to the 
Service (WildEarth Guardians v. Haaland, 2021 WL 4263831 (C.D. Cal. 
September 20, 2021)), ordering us to reconsider whether the two species 
of Joshua tree should be listed under the Act.
    The Service has reassessed its August 2019 12-month finding and 
revised the species status assessment (SSA) report. This document 
complies with the September 20, 2021, court-ordered remand of the 
August 2019 ``not warranted'' 12-month findings for the two species of 
Joshua tree (Yucca brevifolia and Y. jaegeriana) and constitutes our 
new 12-month findings on the September 29, 2015, petition to list the 
Joshua tree species under the Act.

Supporting Documents

    A species status assessment (SSA) team prepared an SSA report for 
Joshua trees (Yucca brevifolia and Y. jaegeriana). The SSA team was 
composed of Service biologists, in consultation with other species 
experts. The SSA report and the information

[[Page 14537]]

reviewed represents compilations of the best scientific and commercial 
data available for the species, including the impacts of past, present, 
and projected future factors (both negative and beneficial) affecting 
the species, that we used to make our determination of status for the 
species.
    In accordance with our joint policy on peer review published in the 
Federal Register on July 1, 1994 (59 FR 34270), and our August 22, 
2016, memorandum updating and clarifying the role of peer review of 
listing actions under the Act, we sought the expert opinions of nine 
appropriate specialists regarding the SSA report for the Joshua trees. 
We received responses from five peer reviewers. We also coordinated 
with the California Department of Fish and Wildlife, Nevada Department 
of Wildlife, Arizona Department of Agriculture's Environmental Services 
Division, and the Utah State Department of Natural Resources and 
Natural Heritage Program during the development of the SSA report for 
the Joshua trees.

Background

Species Information

    In this discussion, we present an overview of the biological 
information for Joshua trees (Yucca brevifolia and Y. jaegeriana). For 
the purposes of this analysis, we discuss both species together using 
the common name--Joshua tree(s)--when the discussion of information 
pertains to both species. Literature or conclusions specific to a 
single species are indicated by the species' scientific name, where 
applicable.
Species Description
    Joshua trees are long-lived plants that occur in desert regions of 
the southwestern United States including portions of California, 
Arizona, Nevada, and Utah, well beyond the Joshua Tree National Park in 
California. Joshua trees are found throughout the Mojave, Great Basin, 
and Sonoran Deserts. Joshua trees have generally been addressed in the 
literature as a single species; however, recent references have 
identified at least two varieties or subspecies (Yucca brevifolia var. 
brevifolia and Y. b. var. jaegeriana). We consider the two entities to 
be two distinct species, the western Joshua tree (Yucca brevifolia) and 
eastern Joshua tree (Y. jaegeriana) based on expert analysis, and we 
treat them as two separate, listable entities. The SSA report has 
additional detailed descriptive information on Joshua trees (Y. 
brevifolia and Y. jaegeriana) (Service 2023, entire).
    Yucca brevifolia--Yucca brevifolia is a 16-40 feet (ft) (5-12 
meters (m)) tall, evergreen, tree-like monocot. The leaves are between 
7.5 and 14.6 inches (in) (19-37 centimeters (cm)) long and are 
clustered in rosettes at the branch ends. Branching only occurs 
following flowering events where one or more lateral shoots develop 
from the base of the inflorescence (cluster of flowers) (McKelvey 1938, 
p. 130; Simpson 1975, p. 32). The flowers on the inflorescence are 
nearly spherical with short, wide petals that curve over the tip of the 
pistil and occur in dense, heavy panicles. Tegeticula synthetica, a 
species of yucca moth, pollinates the flowers; and the resulting seed 
pods require mechanical action (e.g., a rodent) to open and for the 
seeds to be dispersed. In addition to sexual reproduction, the species 
can also reproduce asexually through basal resprouts, particularly when 
under stress. Yucca brevifolia is long-lived (100 to several hundred 
years old), with a generation time of 50 to 70 years.
    Yucca jaegeriana--Yucca jaegeriana is a shorter (9-20 ft; 3-6 m), 
evergreen, tree-like monocot. Yucca jaegeriana has shorter leaves (less 
than 8.7 in (22 cm)) and shorter height to first branching at 2.3-3.3 
ft (0.75-1.0 m) than Y. brevifolia, which results in a denser canopy 
(see figure 3-1 in the SSA report; McKelvey 1938, p. 138; Service 2023, 
p. 9). The flower is elongate with narrow petals that wrap around the 
pistil forming a corolla tube. Tegeticula antithetica, a species of 
yucca moth, pollinates the flowers. The variation in floral morphology, 
specifically style length, between Y. brevifolia and Y. jaegeriana is 
strongly correlated with the physical characteristics of its obligate 
moth pollinator due to coevolution with Tegeticula antithetica having a 
shorter ovipositor than the Y. brevifolia pollinator, T. synthetica 
(see figure 3-1 in the SSA report; Godsoe et al. 2009, p. 820; Yoder et 
al. 2013, p. 11; Service 2023, p. 9). The resulting seed pods require 
mechanical action (e.g., a rodent) to open and for the seeds to be 
dispersed. In addition to sexual reproduction, the species can also 
reproduce asexually through basal resprouts, particularly when under 
stress. Yucca jaegeriana is long-lived (100 to several hundred years 
old), with a generation time of 50 to 70 years.
    Hybrids--Hybrids occur in a smaller geographic area compared to the 
rest of the range, toward Joshua trees' northern limit, where the 
distribution of both species overlap, and are not reliably identifiable 
from morphological characteristics alone (Smith 2022, pers. comm.). The 
hybrid zone was not included in our assessment of viability for Yucca 
brevifolia and Y. jaegeriana, although that zone confers additional 
resiliency, redundancy, and representation to both species.
Taxonomy
    Yucca brevifolia var. jaegeriana was determined to be a distinct 
species based on morphological and pollinator differences (Lenz 2007, 
p. 100) and restriction-site-associated DNA (RAD)-sequencing (Royer et 
al. 2016, p. 1730). These analyses concluded that Y. b. var. jaegeriana 
should be raised to specific rank (Lenz 2007, p. 97) and that it is 
genetically distinct from Y. b. var. brevifolia (Royer et al. 2016, p. 
1736). Additionally, Y. brevifolia diverged at least 5 million years 
ago, possibly due to geographic separation by the Bouse Embayment (a 
Pliocene Era chain of lakes) (Smith et al. 2008a, p. 2682). As 
described above, the two taxa, and their obligate moth pollinators, 
come into contact and plant hybridization occurs in the Tikaboo Valley, 
Nevada, (Starr et al. 2013, p. 4; Royer et al. 2016, p. 136).
    Based on these analyses (Lenz 2007, entire; Smith et al. 2008b, 
entire; Royer et al. 2016, entire), and correspondence between the 
Service and editors of the Jepson Manual (Wallace 2017, p. 2), we 
consider Yucca brevifolia var. brevifolia and Y. b. var. jaegeriana to 
be two distinct species, and we treat them as two separate listable 
entities: Y. brevifolia and Y. jaegeriana, respectively. For additional 
information on Joshua tree taxonomy, see section 3.2 of the SSA report 
(Service 2023, p. 9).

Habitat/Life History

    Joshua trees occur in desert regions of the southwestern United 
States and are located on alluvial fans, plains, and bajadas throughout 
the Mojave, Great Basin, and Sonoran Deserts. Joshua trees occur 
throughout a wide range of vegetation communities between approximately 
1,279 and 8,775 ft (390 and 2,675 m) elevation. Joshua trees are often 
the tallest plants on the landscape where they occur but are not 
typically dominant in terms of vegetation cover. Joshua trees are a 
slow-growing desert plant. Because they do not have growth rings, 
accurately determining the age of Joshua trees is difficult. The height 
of a Joshua tree divided by an estimate of growth per year is used to 
estimate age. Joshua trees can live for several hundred years, though a 
more common lifespan is about 150 years, and have a generation time of 
50 to 70 years. They can reproduce via several mechanisms, have unique 
habitat and ecological needs, and can disperse through environmental 
and biological means.

[[Page 14538]]

Joshua trees' life cycle includes seedling, established individual, 
juvenile, and adult stages (see figure 3-2 in the SSA report (Service 
2023, p. 11)).
    The life history of both Yucca brevifolia and Y. jaegeriana relies 
on a complex set of interactions between individual plants, yucca 
moths, seed dispersers, herbivores/predators, and abiotic conditions 
for successful reproduction and survival to a reproductively mature 
adult (see figure 3-2 in the SSA report (Service 2023, p. 11)). Joshua 
trees reproduce sexually through pollination and seed production as 
well as asexually through vegetative growth (clones). The relative 
contribution of sexual and asexual reproduction and whether the 
proportion varies regionally is not known. The clonal growth strategy 
likely increases persistence of individuals and populations when under 
stress. Optimal reproduction and recruitment of Joshua trees requires a 
convergence of events, including fertilization by its obligate 
pollinators (Pellmyr and Segraves 2003, p. 721), seed dispersal and 
caching by rodents (Vander Wall et al. 2006, p. 543; Waitman et al. 
2012, p. 5), seedling emergence from a short-lived seed bank triggered 
by isolated late-summer rainfall (Reynolds et al. 2012, p. 1652), and 
exposure to cold temperatures that improve seedling and juvenile growth 
and survival (Went 1957, p. 173). For additional information, see the 
SSA report's section 3.4 (Service 2023, p. 10).
Historical and Current Range/Distribution
    Historical Distribution--Joshua trees have occurred in southwestern 
deserts for at least 6 million years (Smith et al. 2008a, p. 255), 
persisting through several geologic time periods characterized by 
variable climate conditions (temperature and precipitation patterns). 
Joshua trees' historical distributions are based on a 2022 empirical 
study conducted throughout the range of Yucca brevifolia and Y. 
jaegeriana and we estimate 9,642,136 acres (ac) (3,903,699 hectares 
(ha)) were occupied historically (see figure 4-1 in the SSA report; 
Esque 2022b, pers. comm.). All areas where adult Joshua trees were 
recorded are considered part of the historical range over an 
approximate time period of 1900 to 1950, based on the lifespan of 
Joshua trees and development trends in the region. Presence, absence, 
and status (alive, dead, or ornamental) of adult Joshua trees were 
assessed through aerial interpretation and ground truthing of aerial 
imagery within quarter square kilometer (500 m by 500 m) grid cells. 
This method could not be applied in the northern portion of the 
species' range near Nellis Air Force Base in southern Nevada. 
Therefore, for the species' range near Nellis Air Force Base, we rely 
on the distribution from the 2018 Joshua tree SSA (Service 2018, p. 
11), which provides the best available data for Joshua tree 
distribution in this area.
    Current Distribution--The current range of Joshua trees extends 
from northwestern Arizona to southwestern Utah west to southern Nevada 
and southeastern California (see figure 4-1 in the SSA report (Service 
2023, p. 31)). Joshua trees are currently distributed over several 
large discontinuous areas totaling 9,447,883 ac (3,825,054 ha) of a 
much larger region. The refined distribution presented in the SSA 
report is based on a 2022 USGS empirical study conducted throughout the 
range of Yucca brevifolia and Y. jaegeriana (Esque 2022b, pers. comm.; 
Service 2023, pp. 30-31). Very little of the historical range has been 
lost; the current distribution of Joshua trees is reduced by 
approximately 3 percent compared to the historical distribution. The 
current distribution is less acreage than we reported in the previous 
2019 SSA report (12,144,840 ac; 4,906,749 ha). The previous 
distribution was based on the records and reports available at that 
time (Service 2019, p. 14). Although our updated current distribution 
is less than previously reported, it is not based on a loss of habitat; 
rather it is an updated estimate of current distribution of the species 
based on new, more accurate, information. Please see sections 4.1 and 
4.2 of the SSA report for further information on Joshua trees' 
historical and current distributions (Service 2023, pp. 30-31).
BILLING CODE 4333-15-P

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[GRAPHIC] [TIFF OMITTED] TP09MR23.014

BILLING CODE 4333-15-C

Species Ecological Needs

    A species' biological condition should be evaluated relative to the 
three conservation biology principles of resiliency, redundancy, and 
representation (Shaffer and Stein 2000, pp. 306-311). Briefly, 
resiliency describes the ability of the species to withstand 
environmental and demographic stochasticity; redundancy describes the 
ability of the species to withstand catastrophic events; and 
representation describes the ability of

[[Page 14540]]

the species to adapt over time to long-term changes in the environment. 
In general, the more redundant, representative, and resilient a species 
is, the more likely it is to sustain populations over time, even under 
changing environmental conditions. Below we describe the population- 
and species-level needs for Joshua trees that were used to evaluate 
resiliency. These concepts will be discussed in more detail in the 
Analytical Framework section below.
Population Needs
    Joshua trees require that habitat and demographic needs are met for 
population resiliency. Joshua trees rely on habitat elements that 
include appropriate substrate, appropriate climatic conditions, yucca 
moth pollinators, rodent seed-caches, nurse plants, and dispersal. 
Appropriate climatic conditions include adequate amounts of annual 
precipitation (4.7-16.9 in (11.8-42.9 cm)), summer monthly 
precipitation in excess of 1.1 in (2.9 cm) in the months of July and 
August, average summer temperatures based on the range experienced 
historically (67 to 91 degrees Fahrenheit ([deg]F); 19.4 to 32.8 
degrees Celsius ([deg]C)), and winter temperatures between 29 and 50 
[deg]F (-1.7 and 10 [deg]C). To reproduce successfully, Joshua trees 
need yucca moth pollinators, nurse plants, and seed-caching rodents. 
The demographic needs that Joshua trees require are survival, 
abundance, recruitment, and dispersal. Sufficient growth and survival 
at all life stages is required for an individual to reach sexual 
maturity and to maintain an abundant population. A diverse age 
structure is important for withstanding variability in climate and the 
pressures of threats such as drought, herbivory, and wildfire because 
young age-classes are more susceptible to mortality during these events 
than adults.
    Joshua trees require populations of sufficient abundance to be 
maintained over time with stable or increasing population growth. 
Sufficient abundance is achieved through survival of young age classes 
to adult, successful reproduction, and recruitment to support the next 
generation. There must be adequate survival at all life stages to 
support an abundant adult population. We currently lack a population 
viability analysis and information on the abundance at each age class 
required to maintain resiliency. Sufficient recruitment is necessary to 
maintain the population over the long term. In particular, seed set 
needs to be high enough to ensure future recruitment considering seed 
predation and the low percentage of viable seed that germinate and 
survive to reproduce. Dispersal of propagules is important for gene 
flow to maintain appropriate levels of genetic variability. Dispersal 
also allows for potential recolonization of sites following 
disturbance. See chapter 5 of the SSA report for further information on 
population needs (Service 2023, pp. 41-50).
    The 2023 SSA report analyzes resiliency within six analysis units 
including two populations of Yucca brevifolia (YUBR North and YUBR 
South), three populations of Y. jaegeriana (YUJA North, YUJA East, and 
YUJA Central), and a hybrid zone (described further in section 4.5 of 
the SSA report (Service 2023, pp. 36-40)). With the exception of the 
hybrid zone, we use these five analysis units to analyze both current 
conditions and future conditions in this document and the SSA report 
(Figure 1, Table 1).

                            Table 1--Summary of Analysis Units Used in the SSA Report
                    [This table appears in the SSA report as table 4-3; Service 2023, p. 37]
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                                         Occupied habitat ac
              Population                         (ha)            Elevation range ft (m)    Land ownership (%) *
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YUBR North...........................  2,129,113 (861,989)....  2,475-8,775 (754-2675).  Federal: 97.6, State:
                                                                                          0.51, Private: 1.6.
YUBR South...........................  2,288,162 (926,381)....  1,922-7,640 (586-2,328)  Federal: 52.3, State:
                                                                                          2.1, Private: 45.6.
YUJA North...........................  2,065,476 (836,225)....  1,540-7,961 (469-2,426)  Federal: 98, State:
                                                                                          0.9, Private: 1.1.
YUJA Central.........................  2,089,163 (845,815)....  1,626-7,627 (495-2,325)  Federal: 91, State:
                                                                                          1.9, Private: 7.9.
YUJA East............................  754,821 (305,595)......  1,279-5,067 (390-1,544)  Federal: 59.8, State:
                                                                                          16.7, Private: 23.5.
----------------------------------------------------------------------------------------------------------------
* Local ownership was less than 1 percent for all analysis units.

Species Needs
    Species needs are an exploration of what influences redundancy and 
representation for Joshua trees. This requires an examination of the 
Joshua trees' evolutionary history and historical distribution to 
understand how Joshua trees function across their range. To maintain 
redundancy, numerous local Joshua tree populations need to be 
distributed widely across the landscape with some degree of 
connectivity to withstand catastrophic events. Finally, to maintain 
representation, which is needed by the species to respond to changing 
environmental conditions, genetic diversity must be maintained by 
preserving populations that are morphologically, geographically, or 
ecologically diverse. In general, Joshua trees need multiple, large, 
sufficiently resilient populations distributed across the range of 
ecological variability to have the redundancy and representation to 
withstand catastrophic events and adapt to environmental change given 
the trees' moderate adaptive capacity. See chapter 5 of the SSA report 
for further information on population needs (Service 2023, pp. 41-50).

Regulatory and Analytical Framework

    Under section 4(b)(3)(B) of the Act (16 U.S.C. 1531 et seq.), we 
are required to make a finding whether or not a petitioned action is 
warranted within 12 months after receiving any petition for which we 
have determined contains substantial scientific or commercial 
information indicating that the petitioned action may be warranted 
(``12-month finding''). We must make a finding that the petitioned 
action is: (1) Not warranted; (2) warranted; or (3) warranted but 
precluded by pending proposals to determine whether any species is an 
endangered species or a threatened species, and expeditious progress is 
being made to add qualified species to the Lists of Endangered and 
Threatened Wildlife and Plants. We must publish a notice of these 12-
month findings in the Federal Register.

Regulatory Framework

    Section 4 of the Act (16 U.S.C. 1533) and the implementing 
regulations in title 50 of the Code of Federal Regulations set forth 
the procedures for determining whether a species is an

[[Page 14541]]

endangered species or a threatened species, issuing protective 
regulations for threatened species, and designating critical habitat 
for endangered and threatened species. The Act defines an ``endangered 
species'' as a species that is in danger of extinction throughout all 
or a significant portion of its range, and a ``threatened species'' as 
a species that is likely to become an endangered species within the 
foreseeable future throughout all or a significant portion of its 
range. The Act requires that we determine whether any species is an 
endangered species or a threatened species because of any of the 
following factors:
    (A) The present or threatened destruction, modification, or 
curtailment of its habitat or range;
    (B) Overutilization for commercial, recreational, scientific, or 
educational purposes;
    (C) Disease or predation;
    (D) The inadequacy of existing regulatory mechanisms; or
    (E) Other natural or manmade factors affecting its continued 
existence.
    These factors represent broad categories of natural or human-caused 
actions or conditions that could have an effect on a species' continued 
existence. In evaluating these actions and conditions, we look for 
those that may have a negative effect on individuals of the species, as 
well as other actions or conditions that may ameliorate any negative 
effects or may have positive effects.
    We use the term ``threat'' to refer in general to actions or 
conditions that are known to or are reasonably likely to negatively 
affect individuals of a species. The term ``threat'' includes actions 
or conditions that have a direct impact on individuals (direct 
impacts), as well as those that affect individuals through alteration 
of their habitat or required resources (stressors). The term ``threat'' 
may encompass--either together or separately--the source of the action 
or condition or the action or condition itself.
    However, the mere identification of any threat(s) does not 
necessarily mean that the species meets the statutory definition of an 
``endangered species'' or a ``threatened species.'' In determining 
whether a species meets either definition, we must evaluate all 
identified threats by considering the species' projected response and 
the effects of the threats--in light of those actions and conditions 
that will ameliorate the threats--on an individual, population, and 
species level. We evaluate each threat and its projected effects on the 
species, then analyze the cumulative effect of all of the threats on 
the species as a whole. We also consider the cumulative effect of the 
threats in light of those actions and conditions that will have 
positive effects on the species, such as any existing regulatory 
mechanisms or conservation efforts. The Secretary determines whether 
the species meets the definition of an ``endangered species'' or a 
``threatened species'' only after conducting this cumulative analysis 
and describing the projected effect on the species now and in the 
foreseeable future.
    In conducting our evaluation of the five factors provided in 
section 4(a)(1) of the Act to determine whether Yucca brevifolia or Y. 
jaegeriana or both species meet the definition of an endangered species 
or a threatened species, we considered and thoroughly evaluated the 
best scientific and commercial information available regarding the 
past, present, and future stressors and threats. We reviewed the 
petition, information available in our files, and other available 
published and unpublished information. Our evaluation may include 
information from recognized experts; Federal, State, and Tribal 
governments; academic institutions; foreign governments; private 
entities; and other members of the public.
    A thorough review of the taxonomy, life history, ecology, and 
threats to Joshua trees is presented in the SSA report (Service 2023, 
entire). Based on the SSA report and information reviewed, we developed 
a species assessment form for the species that contains detailed 
biological information, a thorough analysis of the listing factors, a 
list of literature cited, and an explanation of why we determined that 
the species do not meet the Act's definition of an endangered species 
or a threatened species. This supporting information can be found on 
the internet at https://www.regulations.gov under Docket No. FWS-R8-ES-
2022-0165. The following is an informational summary for the findings 
in this document.

Analytical Framework

    The SSA report documents the results of our comprehensive 
biological review of the best scientific and commercial data regarding 
the status of the species, including an assessment of the potential 
threats to the species. The SSA report does not represent our decision 
on whether the Joshua trees warrant listing as an endangered or 
threatened species under the Act. However, it does provide the 
scientific basis that informs our regulatory decisions, which involve 
the further application of standards within the Act and its 
implementing regulations and policies.
    As discussed above, we used the three conservation biology 
principles of resiliency, redundancy, and representation to assess the 
Joshua trees' viability (Shaffer and Stein 2000, pp. 306-311). Briefly, 
resiliency is the ability of the species to withstand environmental and 
demographic stochasticity (for example, wet or dry, warm or cold 
years), redundancy is the ability of the species to withstand 
catastrophic events (for example, droughts, large pollution events), 
and representation is the ability of the species to adapt to both near-
term and long-term changes in its physical and biological environment 
(for example, climate conditions, pathogens). In general, species 
viability will increase with increases in resiliency, redundancy, and 
representation (Smith et al. 2018, p. 306). Using these principles, we 
identified the species' ecological requirements for survival and 
reproduction at the individual, population, and species levels, and 
described the beneficial and risk factors influencing the species' 
viability.
    The SSA process can be categorized into three sequential stages. 
During the first stage, we evaluated the individual species' life-
history needs. The next stage involved an assessment of the historical 
and current condition of the species' demographics and habitat 
characteristics, including an explanation of how the species arrived at 
its current condition. The final stage of the SSA involved making 
predictions about the species' responses to positive and negative 
environmental and anthropogenic influences. Throughout these stages, we 
used the best available information to characterize viability as the 
ability of a species to sustain populations in the wild over time. The 
SSA report for the Joshua trees (Yucca brevifolia and Yucca 
jaegeriana), January 2023, Version 2, is a summary of the information 
we have assembled and reviewed, and the following is a summary of the 
key results and conclusions based on the SSA report and data evaluated. 
For more detailed information, please refer to the full SSA report, 
which can be found at Docket FWS-R8-ES-2022-0165 on https://www.regulations.gov and at https://www.fws.gov/office/carlsbad-fish-and-wildlife/library.

Foreseeable Future

    The Act does not define the term ``foreseeable future,'' which 
appears in the statutory definition of ``threatened species.'' Our 
implementing regulations at 50 CFR 424.11(d) set forth a

[[Page 14542]]

framework for evaluating the foreseeable future on a case-by-case 
basis. The term ``foreseeable future'' extends only so far into the 
future as we can reasonably determine that both the future threats and 
the species' responses to those threats are likely. In other words, the 
foreseeable future is the period of time in which we can make reliable 
predictions. ``Reliable'' does not mean ``certain''; it means 
sufficient to provide a reasonable degree of confidence in the 
prediction. Thus, a prediction is reliable if it is reasonable to 
depend on it when making decisions.
    It is not always possible or necessary to define the foreseeable 
future as a particular number of years. Analysis of the foreseeable 
future uses the best scientific and commercial data available and 
should consider the timeframes applicable to the relevant threats and 
to the species' likely responses to those threats in view of its life-
history characteristics. Data that are typically relevant to assessing 
the species' biological response include species-specific factors such 
as lifespan, reproductive rates or productivity, certain behaviors, and 
other demographic factors.
    We considered time horizons at mid-century (2040-2069) and end of 
century (2070-2100) for analyzing future conditions for Joshua trees. 
In the SSA report, we developed two future scenarios (Scenario I and 
Scenario II) to help us understand the plausible range of threats and 
their potential impacts on the two Joshua tree species and their 
habitat between now and the end of the century (2070-2099). The two 
scenarios differ in the amount of projected future change in habitat 
loss, invasive grasses, wildfire, and drought and increased 
temperatures associated with climate change. Scenario I modeled future 
conditions as a continuation of current threats under warmer climate 
conditions, an approximate 5.4 [deg]F (3 [deg]C) increase (RCP 4.5) in 
average temperature. Scenario II modeled an increase in threats under 
much warmer climate conditions, an approximate 9 [deg]F (5 [deg]C) 
increase (RCP 8.5) in average temperature. When applying the best 
available information to a listing context in considering what the 
foreseeable future for Joshua trees is, we considered that (1) the data 
sources for invasive grass cover, climate change, wildfire, and 
development provide reliable information without further extrapolation 
for the time period 2050-2070; (2) the species' response to projected 
climate change becomes more uncertain the further out we project 
because we lack information on physiological thresholds; (3) the 
forecasts for occupied habitat begin to diverge around 2050 due to the 
differences in RCP projections (Hawkins 2013, entire; Bamzai-Dodson and 
Rangwala 2019, pp. 31 and 32); and (4) the effects of wildfire at the 
end of the century depend on where wildfires occur and the time between 
fires. Upon subsequent review it was determined that although there are 
climate projections available that project climatically favorable and 
unfavorable areas through the end of century, climate change is the 
only threat where we have reliable information for that time period. 
The best available science for threats to Joshua trees and the species' 
response to projected climate change and wildfire supported evaluating 
future conditions out to 2040-2069 when we can reliably characterize 
the species' response and status, which is a key element in determining 
the foreseeable future. Beyond 50 years, human decisions that affect 
global greenhouse gas (GHG) emissions and the species' response to 
future conditions are a major source of uncertainty (Terando et al. 
2020, pp. 14-15). Therefore, for our evaluation of future condition, we 
rely on the same assumptions about the extent and magnitude of threats 
projected over time in Scenarios I and II of the SSA report for the 
primary threats and consider an earlier time period (2040-2069) along 
the trajectory projected for Scenarios I and II. The data sources and 
rationale that support this decision are summarized below.
    Climate change and wildfire are the primary threats driving the 
future condition of Joshua trees at 2040-2069, which is consistent with 
the primary threats at the end of century in the SSA. Although all the 
bioclimatic models project significant losses of climatically favorable 
habitat, and increased temperatures and drought associated with climate 
change are generally forecasted to have negative effects, the timing 
and magnitude of the species' response to climate change are not well 
established. The literature, in particular bioclimatic models, provide 
information on the potential timing of future climate change without 
sufficient empirical data on physiological thresholds to reasonably 
forecast the magnitude of the species' response or future distribution 
at the end of the century (Hampe 2004, entire; Pearson and Dawson 2004, 
entire; Araujo and Townsend Peterson 2012, pp. 1527, 1528; Garcia et 
al. 2016, pp. 65, 69-72). We consider the bioclimatic models to provide 
an initial inference or working assumption about the potential effects 
of climate change to the Joshua trees based on the limited, available 
information about the two species' response to climate variables (Petru 
and Tielborger 2008, pp. 717, 718, 723-726; Araujo and Townsend 
Peterson 2012, pp. 1527, 1528; Franks et al. 2014, entire; Garcia et 
al. 2016, pp. 65, 69-72; Thompson et al. 2023, pp. 1-7). We note that 
our future projections (2040-2069) are generally consistent with the 
limited available empirical information about Joshua trees' response to 
drought and climate change, and the stable distribution of the two 
species over the last 40 to 50 years under warmer climate conditions. 
Therefore, given the uncertainty of the Joshua trees' response to 
future climate conditions, we did not rely solely on the bioclimatic 
model results for our 2040-2069 projections of Joshua trees' 
distribution.
    There is high uncertainty in the timing and magnitude of the 
species' responses because information about physiological thresholds 
for temperature and other physiological, phenotypic (change in form or 
shape), and genetic responses that may confer tolerance, local 
adaption, and adaptive capacity are unknown, and the potential exists 
for climate refugia in topographically diverse areas. Also, the 
demographic data are not sufficiently reliable to provide an 
understanding of when Joshua tree individuals or populations may begin 
to respond to the effects of climatically unfavorable conditions 
identified in the bioclimatic models and how long adult trees may 
persist in modeled climatically unfavorable conditions at the end of 
century (Thomas 2022, pers. comm; Shafer et al. 2001, p. 207). There is 
limited monitoring data available for a small area of the range of 
Yucca brevifolia in Joshua Tree National Park (the park represents 
approximately 18 percent of the entire range for YUBR). Because we do 
not have historical context to evaluate the data, it is not clear 
whether the site-specific declines noted are an indication of natural 
population variability in this portion of the distribution or the early 
effects of climate change. The best available science indicates that 
both species are long-lived (150-300 years), adapted to hot and dry 
conditions, and have been exposed to a range of environmental 
conditions over thousands of years. Both species continue to occupy 
most of their historical ranges, despite recent increases in 
temperature on the order of 1.8 [deg]F (1 [deg]C) over the last 40 to 
50 years (Figure 4-1 in Service 2023, p. 31). However, we also consider 
the potential loss of occupied habitat in localized

[[Page 14543]]

areas within the warmest and driest portions of the ranges of both 
species. Also, the best available science does not provide information 
on the population dynamics and environmental thresholds for the yucca 
moth species, which are the pollinators for both Joshua tree species. 
Therefore, we presumed that yucca moth populations will track Joshua 
tree flowering, as has been experienced in the past, and the moth will 
experience similar threat effects as described for the Joshua tree 
including recent site-specific declines in Joshua tree National Park. 
We note the high degree of uncertainty regarding these assumptions 
about the Joshua trees' and the yucca moths' responses to climate 
change which introduces uncertainty into our future projections of 
species' status that we cannot quantify at this time; but we have used 
the best available science in developing them, as the Act requires.
    In addition, there is further uncertainty the further into the 
future we project potential effects to both species because future 
climate projections and the rate of warming and maximum exposure 
temperatures varies depending on the global emission trajectory 
evaluated (e.g., RCP 4.5 compared to RCP 8.5) (Knutti and 
Sedl[aacute][ccaron]ek 2013, p. 370). At the end of the century, RCP 
4.5 and 8.5 project an approximate 5.4 [deg]F (3 [deg]C) and 9 [deg]F 
(5 [deg]C) increase in average temperature, respectively; and the 
magnitude of this difference continues to increase through time. 
Therefore, most of the difference between the present climate and the 
climate at 2040-2069 and beyond will be determined by decisions made by 
policymakers today and during the next few years (Terando et al., 2020, 
p. 15). At this time, we have little clarity on what decisions will be 
made by policymakers in the next few decades. Given the long lifespan 
of Joshua trees, combined with uncertainty around future policy, we 
determined the climate projections and the response of Joshua trees at 
the end of century time horizon were too uncertain to make reasonable, 
reliable predictions of future condition. The climate models used in 
the SSA project increases in average summer temperatures of 
approximately 3.6-5.4 [deg]F (2-3 [deg]C) in 2040-2069, depending on 
the location within the Joshua trees' range (Wang et al. 2016, 
unpaginated). This temperature range is slightly less than the future 
climate condition projected in Scenario I of the SSA and within the 
range of variability that Joshua trees have experienced and were 
resilient to in the past. Therefore, we consider the mid-century (2040-
2069) climate projections to be more reliable than end of century 
projections (Hawkins 2013, entire; Bamzai-Dodson and Rangwala 2019, pp. 
31 and 32).
    The data sources evaluated in the SSA also allow us to make more 
reliable projections of the species' response to wildfire for the time 
period 2040-2069. The wildfire models used in the SSA characterized 
current wildfire risk as low to moderate and are considered reliable 
until 2050-2070 (Klinger 2022, pers. comm). Longer term wildfire risk 
is dependent on past fire trends, specifically, where and how 
frequently fires occurred. The best available data provide a range of 
acreage that may burn at the end of the century but do not inform where 
those wildfires might occur or how frequently occupied habitat might 
burn. Therefore, we can more confidently assess the threat of wildfire 
through 2070, based on currently available models. For wildfire, we 
project 12 to 18 percent of the current ranges of Joshua trees to be 
the maximum extent of wildfire at the end of century and we are not 
able to further refine these extents; but we project the maximum extent 
to be less for the time period 2040-2069. Wildfire effects on Joshua 
trees are well documented, and we project effects to be the same as 
analyzed in the SSA and summarized in the threat section below.
    When applying the best available information to develop a 
reasonable and reliable projection of the Joshua trees' future 
condition, the projections of occupied Joshua trees' habitats (i.e., 
future distribution) begin to diverge around 2050 based in large part 
on RCP projections. As we mentioned earlier, after 2040-2069, there is 
too much uncertainty in the amount of occupied habitat based on the 
variability in plausible global emissions trajectories, wildfire risk, 
and the two species' responses for us to make a reliable projection of 
the Joshua trees' future condition. Although our SSA report used future 
scenarios that provide a range of plausible conditions projected to the 
end of century, we determined that projections within the 2070-2099 
timeframe did not provide a reasonable basis to reliably predict the 
impact of future threats and the species' response to them due to the 
identified uncertainties. Regardless of how far into the future we 
could extrapolate the expanding scope of the threats, our confidence is 
greatest at 2040-2069, the period over which we can make reliable 
predictions about threats and the species' response to those threats.

Summary of Biological Status and Threats

    In the following discussions, we review the biological condition of 
the species and their resources, and threats that influence the 
species' current and future conditions, to assess the species' overall 
viability and the risks to that viability. In this section, we 
summarize the Joshua trees' future condition to 2069 when we can 
reliably forecast threats and the species' response to those threats. 
This is a shorter timeframe than we evaluated future scenarios in the 
SSA report. Over the next 47 years (approximately one generation and 
when trees can reproduce sexually), we can reliably characterize the 
Joshua trees' viability where our confidence is greatest with respect 
to the range of projected plausible threats and the species' response. 
There are key areas of uncertainty, primarily regarding the two 
species' response to projected future wildfire and climate conditions, 
that do not allow us to reliably project the Joshua trees' status to 
end of century, as discussed above and in the Finding.

Threats

    In the Joshua tree SSA report, we identified the following threats 
for both Yucca brevifolia and Y. jaegeriana: (1) Habitat loss and 
degradation (from urbanization, military training, renewable energy, 
grazing, and off highway vehicle (OHV) use) (Factor A); (2) invasive 
grasses (Factor A); (3) increased risk of wildfire (Factor A); (4) seed 
predation and herbivory (Factor C); and (5) changing climatic trends 
(e.g., increased temperatures and longer more frequent drought periods) 
(Factor A). Of these threats, we determined that the primary threats or 
those threats which have the capacity to potentially drive any 
population or status trends for the two species are the risk of 
wildfire (Factor A), invasive grasses (Factor A), and climate effects 
(increasing temperature, precipitation changes, drought) (Factor A) 
summarized below both currently and for the foreseeable future (2040-
2069). Because the life history, habitat needs, demographic needs, 
species needs, and general ecology of the two species are congruent, we 
assumed the effects pathways and threat impacts are the same for both 
species. Although habitat loss and degradation (from urbanization, 
military training, renewable energy, grazing, and OHV use) (Factor A) 
and seed predation and herbivory (Factor C) were identified as 
potential threats in the SSA report that may impact individuals or 
portions of the

[[Page 14544]]

population, the best available information indicates that these threats 
have not negatively influenced population dynamics on a population- or 
species-level scale now and are not projected to negatively influence 
population dynamics in the foreseeable future.
    Overutilization (Factor B), disease (Factor C), and small 
population size (Factor E) were not identified as threats in the SSA 
report. In appendix B of the SSA report, we examined the existing 
regulatory mechanisms, regulations, and policies (Factor D) that affect 
the species, including those that relate to climate change (Service 
2023, pp. 152-161). We found that the regulatory mechanisms, such as 
the Clean Air Act (42 U.S.C. 7401 et seq.), which regulates air 
emissions from both stationary and mobile sources, and hazardous air 
pollutants to protect public health, as well as California climate 
policies that help to reduce GHG emissions through the State's Climate 
Adaptation and Resiliency Program (funds projects that provide climate 
adaptation and resilience on California's natural and working lands), 
all contribute toward reduced GHG emissions in the United States. The 
National Environmental Policy Act (NEPA; 42 U.S.C. 4321 et seq.) also 
provides some protections for listed species that may be affected by 
activities undertaken, authorized, or funded by Federal agencies, which 
may result in the development of avoidance and mitigation measures for 
the threats that affect special status species. For the purposes of 
this document, the primary threats are the focus of the threats 
discussion for the two species which are summarized below both 
currently and for the foreseeable future (2040-2069). For a complete 
description of all the threats and existing regulatory mechanisms, 
refer to chapter 6 and appendix B of the SSA report (Service 2023, pp. 
50-87, 152-161).

Habitat Loss and Degradation

    The loss of habitat and degradation by urbanization, military 
training, renewable energy development, grazing, and OHV use are 
occurring in varying degrees across the range of the Joshua trees and 
are currently considered a low magnitude threat. The higher severity 
impacts of urbanization, military training, and renewable energy 
development are localized and have a limited scope in terms of acreage 
of impacts and the analysis units where they occur. The YUBR South 
analysis unit is most affected by habitat loss and degradation both now 
and in the future due to its proximity to larger, metropolitan centers 
with increased development and edge effects, along with the amount of 
the analysis unit that is privately owned (45.6 percent), designated 
for renewable energy development, and subject to military training. 
Privately owned landownership is low (7 percent) throughout the range 
of Yucca jaegeriana and is highest in YUJA East (23.5 percent). No 
information was available to categorize the threat of renewable energy 
development in Arizona, Nevada, and Utah. Grazing and OHV use are more 
widespread, but the intensity of the impacts is currently low and 
diffuse; and impacts are projected to remain low and diffuse in the 
future.
    The best available information indicates that substantial habitat 
loss due to development, military training, or renewable energy 
development is unlikely in the foreseeable future. Habitat loss due to 
development was projected for 2060 based on the average of two models 
available through the Integrated Climate and Land Use Scenarios (ICLUS) 
database for RCP 4.5 and 8.5 (Environmental Protection Agency 2015) to 
be less than 8 percent of the current distribution of Yucca brevifolia 
and less than one percent of the distribution of Y. jaegeriana. In 
addition, estimates include 2040-2069 projections for renewable energy 
development in California for Y. brevifolia (approximately 100,000 ac; 
40,469 ha), based on the acreage of current and permitted projects that 
is forecasted to be approximately half the development projected for 
the end of century (Service 2023, pp. 53). However, we lacked 
sufficient information to project renewable energy development outside 
of California. Habitat loss is forecasted to be a low-magnitude threat 
in the future.
    In addition, impacts to Joshua trees are avoided, minimized, or 
mitigated on Federal lands and within several jurisdictions in 
California to varying degrees as discussed in appendix B and section 
6.1.6 of the SSA report (Service 2023, pp. 57, 152-161). We anticipate 
that these measures and regulations will continue to address potential 
losses in that region now and in the future, particularly on military 
and federally managed lands, which currently account for 74 percent of 
the current distribution of Yucca brevifolia and 89 percent of the 
distribution of Y. jaegeriana (Table 4-1 in Service 2023, p. 33). 
However, in Arizona, Nevada, and Utah, there are fewer regulatory 
protections in place on private land, though private land in these 
states represents a small percentage of the species' range. Overall, 
these effects are localized and constitute a small portion of the 
range, such that they are not likely to have a population- or species-
level impact. Therefore, there is no indication that current or future 
effects (2040-2069) resulting from habitat loss and degradation by 
urbanization, military training, renewable energy development, grazing, 
or OHV use, or a combination of these, would significantly reduce the 
redundancy, representation, or resiliency of Y. brevifolia or Y. 
jaegeriana. See chapter 6 of the SSA report for more detailed 
information (Service 2023, pp. 50-87).

Wildfire

    Wildfires are not historically a common occurrence in the desert 
regions of the southwestern United States. Due to the low, 
discontinuous vegetative cover and fuel loads, wildfires are typically 
infrequent and small in size (Brooks and Matchett 2006, p. 148). Fire 
return intervals of greater than 100 years or more were estimated for 
Artemisia tridentata (Great Basin sagebrush) plant communities in the 
Southwest, and similar historical return intervals or longer are 
presumed for the range of Joshua trees (Mensing et al. 2006, p. 75). As 
a result, native scrub vegetation communities in the desert Southwest, 
including Joshua trees, have not evolved with wildfire and are 
generally considered to not be well-adapted to fire (Abella 2010, p. 
1249). Wildfires may cause numerous potential direct and indirect 
effects on Joshua trees and the associated plant community, including 
immediate mortality, reduced survivorship over time, loss of nurse 
plants, reduced native cover, lower native plant diversity, damage to 
the protective bark-like periderm, mortality of the seed bank, and 
potential disruption of the pollinator and rodent communities. Joshua 
trees' habitat is estimated to require approximately 100 years to reach 
densities, cover and stature similar to pre-burn conditions, though 
nurse plant cover and the understory may attain pre-burn conditions in 
as little as a few years to several decades depending on whether the 
root crown survives (Minnich 1995, p. 104). Wildfires also promote 
colonization by invasive grasses, discussed further below.
    The magnitude of the impact varies with the size, severity, and 
frequency of wildfires; amount of invasive grass cover; and weather 
conditions both during and after the event (DeFalco et al. 2010, 
entire; Barrios et al. 2017, entire; Klinger et al. 2019, p. 10). 
Joshua tree mortality can be high following wildfire (64 to 95 percent) 
with increased impacts to young age-classes

[[Page 14545]]

and when wildfires were followed by drought conditions (Minnich 1995, 
p. 102; DeFalco et al. 2010, p. 246). Habitat recovery is similarly 
impacted by subsequent climate conditions and may take 100 years to 
reach densities, cover, and stature similar to pre-burn conditions 
(Minnich 1995, p. 104), though habitat recovery may be sooner in low 
severity wildfires where individual trees persist and can reproduce 
(flower and resprout) under appropriate climate conditions. Joshua 
trees also may respond to wildfire by producing resprouts from the 
trunk or from the primary roots (Minnich 1995, p. 102; Barrios et al. 
2017, p. 103; St. Clair et al. 2022, p. 4). Resprouting requires the 
tree or root system to be viable post-fire. Resprouting is more 
frequent in areas with a high proportion of surviving trees and 
decreases with increasing burn severity (Minnich 1995, p. 103). 
Resprouting and the clonal growth strategy increases persistence of the 
individual under stress, such as wildfire (Rowlands 1978, p. 50; 
Harrower and Gilbert 2021, p. 11; Esque 2022a, pers. comm.), and 
facilitates the ability of Joshua trees to continue to occupy habitat 
even when the main stem has died. Also, within the burn perimeter, 
small patches with trees, nurse plants, and a seedbank may persist to 
facilitate recovery of the species and its habitat post-fire (Klinger 
2022, pers. comm.).
    The wildfire risk and potential impacts to Joshua trees were 
characterized based on low (less than 4,000 ft; 1,200 m), middle 
(4,000-6,000 ft; 1,200-1,800 m) or high (greater than 6,000 ft; 1,800 
m) elevation plant communities (see table 6-1 and appendix D in the SSA 
report (Service 2023, pp. 67, 165; Klinger et al. 2019, entire)). Low 
elevations tend to have low severity fires due to low vegetative cover. 
In areas subject to low severity fire, adult Joshua trees have a lower 
probability of dying from direct mortality, and trees may avoid being 
burned due to their taller stature, particularly for Yucca brevifolia. 
However, repeated low severity events promoted by invasive grasses 
contribute to increased charring over time that can increase the risk 
of mortality, particularly to young plants that are more vulnerable to 
fire. Middle elevation vegetation communities are correlated with 
increasing fires, acres burned, and the invasive grass-wildfire cycle 
(Brooks and Matchett 2006, pp. 153, 155). The invasive grass-fire cycle 
is well documented in the literature as a positive feedback loop, and 
invasive grasses alter the fire regime in several ways (discussed 
further in section 6.3 of the SSA report (Service 2023, pp. 60-70)). 
Middle elevations typically have a higher fuel load, with sufficient 
native vegetative cover to carry fires; therefore, wildfires can be 
more severe and are often associated with increased invasive grass 
cover. Moderate severity burns may result in adult mortality and are 
projected to char trees, including singeing the crown, which may 
contribute to increased mortality and decreased tree densities over 
time. In moderate severity burns, nurse plants may be burned and die, 
and the Joshua tree and nurse plant seedbank may also be negatively 
impacted. Though fires are less frequent in high-elevation vegetation 
communities with heavier fuels, when they do occur, wildfires tend to 
have higher severity and can result in direct tree mortality or alter 
the subsequent vegetation composition and cover. However, most Joshua 
trees occur in low and middle elevation vegetation communities that are 
unlikely to experience high severity burns.
    Based on the wildfire history and modeled wildfire risk, increased 
wildfires are an imminent, low-to-moderate magnitude threat currently 
and in the foreseeable future (2040-2069). Since 1960, only 9 percent 
of the total acreage across the range of Joshua trees has burned, 
including 24 percent of the YUJA North analysis unit. We project 
recovery of the species and habitat to take up to 100 years in areas 
that do not have an altered invasive grass-wildfire cycle. The modeled 
risk of wildfires and the modeled wildfire regimes are estimated for 
current and future conditions through approximately 2070 (Klinger et 
al. 2021, entire). We project that the acreage of the range of both 
species of Joshua tree that will burn in 2040-2069 will be less than 
our end of century projections of 12 to 18 percent of the range of both 
species of Joshua tree; this estimate is based on a moderate increase 
in the acreage that has burned in the last 50 years (9 percent on 
average), and wildfires are more likely to occur in areas that have 
previously burned (Klinger 2022, pers. comm.). Although the risk of 
wildfires was modeled, there is uncertainty in where wildfires will 
occur, how the fire return interval will be affected, and how often 
high frequency fires will occur; although increased impacts from 
wildfire are projected for middle- and high-elevation plant 
communities. We project the potential for tree mortality, reduced tree 
densities, and limited recruitment following wildfires, while the 
habitat recovers. Post-fire habitat recovery may occur more quickly in 
more mesic areas; but the time required for recovery may be extended 
beyond 100 years due to drought conditions.
    Overall, there is limited evidence of the invasive grass-wildfire 
cycle currently but it is most prevalent in the northern portion of the 
range of Yucca jaegeriana. Yucca jaegeriana is also at higher risk of 
wildfires due to a high proportion of the analysis units with estimated 
high ignition probability, fire frequency, and burn severity. Areas of 
predicted high burn severity occur near predicted high frequency 
wildfire areas, increasing the probability of large wildfire events 
that could impact Joshua trees. Wildfire is a low magnitude threat in 
YUJA East because this area is at low elevation with lower vegetative 
cover and a low probability of natural ignitions.
    The risk of wildfires is a low to moderate threat throughout the 
range of Yucca brevifolia and lower than for Y. jaegeriana. YUBR North 
is at moderate risk for a moderate- to high-severity fire that could 
alter the vegetation composition and cover in areas adjacent to higher 
invasive grass cover. The probability of natural ignition is lower in 
this analysis unit, but there are population centers and high areas of 
visitation that are likely to increase human-caused ignitions. YUBR 
South is also considered to be at moderate risk. Approximately 9 
percent of the analysis unit has burned in the last 50 years, but most 
of the analysis unit is at low elevation with wildfire risk 
characterized by low frequency and severity. Ignition sources may be 
higher than predicted in the models due to the high frequency of 
wildfires along the urban-wildland interface consistent with 
correlations between increasing human population density and fire 
ignitions (Keely and Fotheringham 2001, p. 1541).
    Under projected future climate conditions, areas previously burned 
have a high probability of being colonized by invasive grasses, 
particularly cheat grass in the north and northeast, and the elevation 
limit of the distribution of invasive grasses may increase with 
increasing temperatures and the potential for increased fire frequency. 
We forecast vegetation cover to decrease at lower elevations over time 
with extended droughts and increased fire frequency in previously 
burned areas, particularly to the east and northeast, though extreme 
rainfall events have the potential to reestablish high invasive grass 
cover. Overall, we project there to be a high probability of large, 
infrequent, high severity wildfires at middle and high elevations in 
areas

[[Page 14546]]

that have not burned, and lower potential and frequency of wildfires at 
low elevations. Small patches of unburned habitat may remain within 
burned areas at middle- and high-elevation zones due to topographic 
heterogeneity and hydrological refugia.
    We are not able to accurately predict areas that will burn in the 
future; however, we project areas that burn once at low to moderate 
severity may recover slowly (up to 100 years post-burn) and continue to 
support Joshua trees. We project high severity fires and areas that 
burn repeatedly are not likely to support the species in the future 
(Klinger 2022, pers. comm.). Both species occur mostly on Federal lands 
and existing regulatory mechanisms include BMPs to help protect against 
wildfire (see Conservation Measures and Existing Regulatory Mechanisms, 
below, and appendix B of the SSA report (Service 2023, pp. 152-161)).
    After examining the extent and impact of the risk of wildfire, we 
project that wildfire conditions in 2040-2069 will be similar or 
slightly increased relative to current conditions. We determined that 
while this threat could occur throughout the range, our projections 
indicate less than 12 to 18 percent of the ranges of the Joshua trees 
may be at risk of burning by 2040-2069, including areas that have 
burned previously. Due to the limited portions of the ranges that are 
anticipated to burn and fire suppression efforts that are implemented 
on Federal lands, the threat of wildfire would be unlikely to impact 
either of the two species at a population- or species-level scale. The 
threat of wildfire does not have the projected extent to drive any 
declines in status trends for the two species during our evaluation 
period. As a result, there is no indication that the current or future 
effects of wildfire would significantly reduce the redundancy, 
representation, or resiliency of Yucca brevifolia or Y. jaegeriana. See 
chapter 6 of the SSA report for more detailed information (Service 
2023, pp. 50-87).

Invasive Annual Grasses

    Nonnative plant species, particularly invasive grasses spread by 
humans and anthropogenic disturbance, have the potential to 
substantially degrade desert habitats and affect the frequency of fire. 
The potential effects to Joshua trees include competition, 
perturbations in the natural disturbance and fire regime, plant 
community composition, vegetation structure, and a microclimate shift 
(Gordon 1998, p. 976). The severity of the nonnative plant invasion is 
dependent on the influence of local site factors including soil type, 
elevation, and disturbance history (Chambers 2000, pp. 1403-1412; 
Gelbard and Belnap 2003, p. 429; Chambers et al. 2007, entire; Davies 
2008, pp. 113-114; Chambers et al. 2013, entire; Davies and Hulet, 
2014, pp. 1-2). Disturbed soils provide additional safe sites for weed 
establishment, and the removal of the existing vegetation alleviates 
resource competition and promotes the successful invasion of weeds 
(Case 1990, pp. 9610, 9613-9614; Masters and Sheley 2001, p. 505; Novak 
and Mack 2001, p. 115; Leonard 2007, pp. iii, 61-62; Hornbeck et al. 
2019, entire). Once established, invasive grass cover can increase 
rapidly in response to rainfall, particularly periods of high winter 
precipitation typical of El Ni[ntilde]o oscillation events and 
following wildfire (Brooks and Machett 2006, p. 149). In the future, 
invasive grasses have the potential to expand their competitive edge 
over native species and benefit under conditions of drought, increased 
carbon dioxide concentration, extreme precipitation events, and 
atmospheric nitrogen (Archer and Predick 2008, p. 25). As a result, 
invasive grasses are projected to increase in the future, particularly 
in disturbed or burned areas, although they may be constrained by 
extended drought, with the potential to shift toward longer fire return 
intervals in the most arid areas of the Mojave Desert (Comer et al. 
2013, p. 7).
    There are no published studies on the competitive effects of 
nonnative plant species to the germination, growth, and reproduction of 
the Joshua trees; however, we project competitive effects to increase 
with increasing nonnative plant cover and seedlings to be the most 
vulnerable life stage if they share the same root niche space and their 
soil water needs are high at a time of active nonnative plant growth 
and reproduction (Schwinning and Kelly 2013, pp. 888, 894; Craine and 
Dybzinksi 2013, pp. 837, 839; Gioria and Osborne 2014, pp. 5-6). The 
largest, potential negative effect of nonnative invasive grasses to the 
Joshua trees is their contribution to wildfire risk and an altered 
wildfire regime (see Wildfire, above; Brooks and Matchett 2006, p. 149; 
Service 2023, pp. 60-70).
    We evaluated the potential for nonnative plant species to 
contribute to the risk of wildfire and an altered fire regime within 
Joshua trees' habitat based on information on the abundance (in terms 
of percent cover) of invasive grasses including cheatgrass (Bromus 
tectorum), red brome (Bromus rubens), and other invasive grasses). 
Currently, invasive grasses are present in approximately half of the 
Joshua trees' habitat. We categorized 37 percent (3,539,813 ac; 
1,432,511 ha) of the range as low abundance (based on the threshold of 
less than 15 percent cover of invasive grasses) and 12 percent 
(1,176,966 ac; 476,301 ha) of the range as high abundance (greater than 
15 percent cover), based on the Bureau of Land Management (BLM) Rapid 
Ecological Assessment (REA) models of potential invasive grass cover 
for 2025 (Comer et al. 2013, p. 10). We defined these categories based 
on several studies; although low levels of invasive grasses may 
increase the risk of fire (Comer et al. 2013, p. 78), higher cover is 
needed to sustain wildfires and alter the natural fire regime 
consistent with our high abundance category (Link et al. 2006, pp. 114, 
116). YUJA North has the greatest proportion of habitat characterized 
as high abundance (30 percent), followed by YUBR North (15 percent). 
Areas of high abundance of invasive grass cover tend to occur along the 
interface between the Mojave and Central Basin and Range ecoregions 
near the northern limit of Yucca brevifolia and Y. jaegeriana 
distribution and represent 7 percent of the ranges of Joshua trees (see 
figure 6-2 in the SSA report (Service 2023, p. 62)). Throughout the 
range of Joshua trees, high abundance areas are located in recently 
burned areas and along the urban-wildland interface (Comer et al. 2013, 
p. 79).
    Although invasive grasses are highly pervasive and beyond the 
ability of any agency to eradicate, they and other nonnative plant 
species are managed on Federal and State lands to varying degrees. In 
particular, more than half of the distribution of Joshua trees occurs 
on BLM land (54 percent). BLM has best management practices (BMPs) for 
invasive and nonnative species that focus on the prevention of further 
spread and/or establishment of these species (BLM 2008, pp. 76-77). 
BMPs should be considered and applied where applicable to promote 
healthy, functioning native plant communities, or to meet regulatory 
requirements. BMPs include inventorying weed infestations, prioritizing 
treatment areas, minimizing soil disturbance, and cleaning vehicles and 
equipment (BLM 2008, pp. 76-77).
    Invasive grasses are a low to moderate, pervasive, ongoing threat 
that affects approximately half of the range of Joshua trees to some 
degree. The severity ranges from low to moderate depending on the cover 
and is highest in YUJA North and YUBR North. In the future (2040-2069), 
invasive grasses are projected to expand their competitive edge over 
native species and are likely to benefit under conditions of drought,

[[Page 14547]]

increased carbon dioxide concentration, extreme precipitation events, 
and atmospheric nitrogen (Archer and Predick 2008, p. 25). As a result, 
we predict that the threat of invasive grasses will increase, although 
extended droughts have also been hypothesized to result in decreased 
biomass and the potential to shift toward longer fire return intervals 
in the most arid areas of the Mojave Desert (Comer et al. 2013, p. 7). 
Using the BLM REA models described above, as well as modeled future 
invasiveness from the same publication, minor increases in invasive 
grass cover are projected for 2040-2069. Low invasive grass cover 
increased by approximately 5 percent as areas with no previous invasive 
grass cover become invaded; and the acreage at high risk increased by 1 
percent to 13 percent of the range of Joshua trees.
    After examining the extent and rangewide impact of invasive grasses 
on Joshua tree, we determined that invasive grasses are a low magnitude 
threat. Projected impacts are low throughout approximately 80 percent 
of the Joshua trees' range where invasive grasses are not present or 
occur in low abundance currently and are projected to remain at low 
abundance in the future. A smaller portion of the range (approximately 
12 to 13 percent) currently has or is projected to have a higher 
abundance of invasive grass and moderate degree of threat affecting 
these localized areas, particularly to the north and northeast in 
burned habitat and along the urban interface. The effect of invasive 
grasses on competition, soil moisture, and vegetation community 
composition and structure is not currently influencing population- or 
species-level dynamics, and we do not project effects to increase in 
the future in unburned, intact habitat. This threat individually is 
unlikely to drive any declines in status trends for either species in 
the future except in developed or burned habitat. The contribution of 
invasive grasses to the increased risk of wildfire is discussed above. 
As a result, there is no indication that the current or future effects 
of invasive grasses associated with competition with Joshua trees or 
potential effects on habitat structure would significantly reduce the 
redundancy, representation, or resiliency of Yucca brevifolia or Y. 
jaegeriana. See chapter 6 of the SSA report for more detailed 
information (Service 2023, pp. 50-87).

Climate Change

    Temperatures have been increasing in the desert southwest for 
decades; since 1950, the region experienced hotter temperatures than in 
any period during the past 600 years (Garfin et al. 2014, p. 464). 
Current summer temperatures (1991-2010) have increased by approximately 
1[deg]C relative to historical temperatures (1961-1990) (figure 6-5 in 
Service 2023, p. 72; Wang et al. 2016, unpaginated). The southwestern 
United States is projected to be affected particularly severely by 
prolonged drought, fewer frost days, warmer temperatures, greater water 
demand by plants, and an increase in extreme weather events (Archer and 
Predick 2008, pp. 23-24; Cook et al. 2015, entire; Jepson et al. 2016, 
p. 49). For Yucca brevifolia and Y. jaegeriana, the main threats 
associated with the current and future effects of climate change are 
temperature increases (increasing maximum summer temperatures and 
increasing minimum winter temperatures), changes in summer and winter 
precipitation, and prolonged drought that contribute to increased 
drought stress. Climate models forecast an increase in the variability 
of precipitation, including the potential of high precipitation events 
generally tied to El Ni[ntilde]o-Southern Oscillation and the potential 
increase of prolonged drought conditions in the intervening period. 
Increasing temperatures may increase moisture stress on adults, 
potentially limit flowering at lower elevations, and may limit seedling 
survival and establishment. The most dramatic temperature increases are 
predicted to occur along the southern edge of the two species' ranges, 
at lower latitudes and elevations such as in YUJA East, which is warmer 
on average than the rest of the analysis units. Similarly, YUBR South 
is currently experiencing higher moisture stress in areas with recent, 
localized observations (from a 12-year period) of reduced recruitment 
and survival, though we lack historical data to confirm a declining 
trend. YUJA East is already experiencing the warmest cold season 
temperatures under current conditions within its range (see section 
5.1.5 in the SSA report (Service 2023, p. 44)) and is projected to be 
warmer in the future, potentially resulting in reduced seedling growth 
and establishment (see figure 6-5 in the SSA report (Service 2023, p. 
72)). Overall, the pattern of increasing drought stress is likely to 
occur across all analysis units to varying degrees depending on 
elevation and latitude. Forecasted changes in climate conditions also 
have the potential to influence or exacerbate other threats such as 
increased risk of wildfire. See chapter 6 of the SSA report for more 
detailed information (Service 2023, pp. 70-80).
    We evaluated current and projected changes in climatic parameters 
averaged across 13 general circulation models from the Climate Model 
Intercomparison Project 6 (CMIP6) (Mahoney et al. 2003, entire) 
compiled using the ClimateNA tool (version 7.21, https://climatena.ca/) 
(Wang et al. 2016, entire). We also evaluated six Joshua tree-specific 
bioclimatic models that forecast the degree to which the current 
species' range will contain the same climate conditions for both 
species in the future (2040-2069) or where parts of the species' ranges 
will not support current climatic conditions, referred to as 
climatically unfavorable throughout the rest of the document (Shafer et 
al. 2001, entire; Dole et al. 2003, entire; Cole et al. 2011, entire; 
Thomas et al. 2012, entire; Barrows and Murphy-Mariscal 2012, entire; 
Sweet et al. 2019, entire). We did not thoroughly address these models 
in the 2018 Joshua tree SSA report because earlier models used coarse-
scale climate data and the most recent model, using smaller-scale 
climate data, was limited to a relatively small portion of the Joshua 
trees' range and, at the time, we determined that the data could not be 
extrapolated to the entire range due to the lack of demographic data. 
Since our last review, additional bioclimatic models were evaluated 
that support the earlier models. However, two of these models used 
finer-scale data and identified the potential for climate refugia in 
topographically diverse habitat that does not appear to have been 
captured in the coarse-scale climate models. We evaluate the combined 
results of these bioclimatic models below (see also table 6-3 of the 
SSA report (Service 2023 p. 82)).
    There is consistency across the bioclimatic models that the 
southern portion of the ranges of both species and lower elevation 
habitat areas may not support current climate conditions for Joshua 
trees in the future. The models forecast that 66 to 88.6 percent of the 
current range will be climatically unfavorable, meaning different than 
the current climate conditions that Joshua trees occupy, in 2040-2069. 
However, these models do not include estimates of Joshua trees' future 
distribution and the best available science does not provide 
physiological temperature thresholds to inform the timing and magnitude 
of the species' response and when species viability may be affected, as 
we discussed earlier (see Foreseeable Future, above), though we 
acknowledge the potential for long-term negative effects to both 
species. The best available science indicates that both

[[Page 14548]]

species are long-lived (150-300 years), adapted to hot and dry desert 
conditions, and have been exposed to extreme and variable climate 
conditions over thousands of years. Also, individual adult trees have 
experienced a range of environmental conditions over the typical 
lifespan of 100 to several hundred years. Both species also continue to 
occupy most of their historical ranges, despite recent increases 
(approximately 1.8 [deg]F (1 [deg]C)) in average summer temperatures 
over the last 40 to 50 years (Figure 4-1 in Service 2023, p. 31).
    Joshua trees are projected to experience increases in average 
summer temperature of approximately 3.6-5.4 [deg]F (2-3 [deg]C) by 
2040-2069, depending on the location (Wang et al. 2016, unpaginated). 
These temperature ranges are anticipated to be within the range of 
variability that Joshua trees have experienced in the recent past. 
Therefore, we consider that the majority (approximately 90 percent) of 
the current range of both species will continue to be occupied and 
viable in 2040-2069 and acknowledge the potential for the localized 
loss of occupied habitat in the warmest and driest portions of the 
ranges of both species. In the last decade several masting events 
(large flowering events where the majority of trees within a region 
flower) were recorded despite recent temperature increases, even at the 
southern limit of their distribution (Service 2023, p. 79); and we 
project masting events to continue to occur throughout the majority of 
the ranges of both species. Modeled climatically unfavorable areas, 
areas projected to experience warmer and drier climate conditions than 
current climate conditions, may have reduced ability to support species 
needs with the potential for reduced growth, lower recruitment, 
increased predation, and tree mortality that may contribute to 
localized losses at low elevations and latitudes. We cannot reliably 
assess or characterize the degree of reduction in these demographic 
parameters; but we do assume and project that recruitment will be 
reduced throughout portions of the currently occupied habitat modeled 
as climatically unfavorable in 2040-2069 (66-88.6 percent) based on a 
projected increase of approximately 3.6-5.4 [deg]F (2-3 [deg]C)(Barrows 
and Murphy-Mariscal 2012, entire; Thomas et al. 2012, entire). We 
project recruitment will be reduced relative to current conditions; we 
assumed no to low recruitment for the warmest and driest portions of 
the range and an increasing reliance on clonal growth to support 
occupancy and viability.
    The potential effects of increasing temperatures and drought on 
Joshua trees' habitat are complex and are dependent on the direct 
effects of future climatic conditions described above, as well as the 
strength and magnitude of the interaction with their specialist 
pollinators, the yucca moths, and rodent seed dispersers. In the last 
decade several mast flowering events were recorded despite recent 
temperature increases, even at the southern limit of their distribution 
(Service 2023, p. 79), though there is a limited understanding of yucca 
moth abundance during these events. Overall, the best available science 
does not include information on the population dynamics and 
environmental thresholds for the yucca moth species rangewide. 
Therefore, we presumed that yucca moth populations will track Joshua 
tree flowering, as has been experienced in the past, and will 
experience similar threat effects as described for the Joshua tree. We 
note that there is a high degree of uncertainty regarding these 
assumptions which limits our ability to reliably project the Joshua 
trees' future condition beyond 2040-2069. Prolonged drought conditions 
may increase seed predation and herbivory as water and food resources 
are limited; and we project that drought and drought-exacerbated seed 
predation and herbivory may increase in the future. Currently there is 
evidence of localized effects of predation and herbivory; but the best 
available science does not support the potential for population- or 
species- level effects currently or in the future. Prolonged droughts 
may have the potential to reduce rodent populations due to limited 
availability of water and food resources, but we have no reliable means 
to evaluate future climate effects to the suite of rodents that forage 
on Joshua trees nor future changes in seed dispersal. Recent mast 
flowering events in the last decade appeared to satiate rodent 
populations (Service 2023, p. 79); but any projections that we would 
develop about the future predation and herbivory effects to Joshua 
trees or future seed dispersal would be speculative.
    The existing regulatory mechanisms in place help protect habitat 
and provide protective measures for Joshua trees; however, few 
regulations specifically address the threat of climate change (see 
appendix B of the SSA report (Service 2023, pp. 152-161)). Therefore, 
while existing regulatory mechanisms and current conservation efforts 
may contribute to reduced GHG emissions in the United States, impacts 
from climate change are forecasted to increase in the future.
    The cumulative effects of climate change are complex and ongoing. 
Currently, climate change is a low-to-moderate magnitude threat with 
primarily localized effects on individual Joshua trees and portions of 
populations; there is no indication that climate change is currently 
reducing redundancy, representation, and resiliency of the Joshua 
trees. There is the potential for higher magnitude effects in the 
future, particularly for habitat at low elevation and latitudes along 
the southern edge of the Joshua trees' ranges. Based on the best 
available science we project that Joshua trees will still occupy and 
maintain viability in the majority of the species' current distribution 
in 2040-2069. Therefore, we project climate change over this time 
period to be a low to moderate magnitude threat in the foreseeable 
future with the greatest impacts at lower latitudes and elevations. 
Forecasted reductions in recruitment may decrease resiliency in 
portions of populations but there is no indication that climate change 
will result in a reduction in redundancy and representation that would 
impact the viability of the species through the years 2040-2069.

Summary of Threats

    We evaluated the current threat of habitat loss and degradation, 
invasive grasses, increased risk of wildfire, climate change, and 
predation and herbivory within the distribution of Joshua trees, 
including how threats varied by analysis unit (see table 6-4 of the SSA 
report (Service 2023, p. 86)). Habitat loss and degradation is 
generally focused in localized areas within the range of Joshua trees 
and is currently considered a low magnitude threat overall and across 
each of the analysis units, despite the intensity of impacts being 
potentially severe in some localized areas. In the future, we project 
the threat of habitat loss and degradation to increase, but the effects 
will continue to be localized.
    We consider invasive grasses to have a low-to-moderate potential 
threat to degrade habitat; moderate potential threat was defined in 
analysis units with approximately 12 to 13 percent of the area with 
high invasive grass abundance. Our analysis indicated that there is 
evidence of an invasive grass-wildfire cycle currently in the northern 
range of Yucca jaegeriana. Wildfire models estimate an increase in the 
frequency of wildfires to the northeast and high likelihood of more 
severe fires at northern latitudes and higher elevations, although the 
area anticipated

[[Page 14549]]

to burn is likely to be less than 12 to 18 percent (including areas 
previously burned). Current climate conditions are warmer than 
historical climate conditions and warmer climate conditions may be 
increasing drought stress at lower elevations. It is not clear from the 
limited monitoring data (from a 12-year period) if YUBR South, the 
southernmost and warmest analysis unit, is experiencing a declining 
trend caused by climatic conditions or if it is experiencing a natural 
fluctuation in population. We do not have information on the effect of 
warmer climate conditions and the current mega-drought in the rest of 
the species' range; but masting reproductive events continue to occur 
several times a decade, even in the southern portion of the ranges of 
both Joshua tree species. Therefore, we consider climate change a low-
to-moderate threat. Predation and herbivory are considered a low-to-
moderate potential threat across the species' range. Several 
regulations, planning documents, and management plans in place help 
ameliorate the magnitude of these threats on Joshua trees and are 
further described in appendix B of the SSA report (Service 2023, pp. 
152-161). Cumulatively, these threats are not projected to result in 
population- or species-level declines by 2040-2069, because the 
majority of the range of both species is projected to remain occupied 
and viable (Service 2023, figure 6-5, p. 87; Wang et al. 2016, 
unpaginated).

     Table 2--Summary of the Current and Future (2040-2069) Magnitude of the Threats * to Joshua Tree Based on the Scope, Intensity, Likelihood, and
                                                                        Immediacy
                                   [Service 2023, p. 51]. [This table appears in the SSA report as table 6-5 (p. 87)]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                         Habitat loss and                                                                               Predation and
     Population/analysis unit               degradation            Invasive grasses      Risk of wildfires       Climate change           herbivory
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                    Yucca brevifolia
--------------------------------------------------------------------------------------------------------------------------------------------------------
YUBR North........................  Low.......................  Low to Moderate......  Moderate.............  Low to Moderate.....  Low.
YUBR South........................  Low +.....................  Low..................  Moderate +...........  Moderate +..........  Low to Moderate +.
YUBR Summary......................  Low.......................  Low to Moderate......  Low to Moderate......  Low to Moderate.....  Low to Moderate.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                    Yucca jaegeriana
--------------------------------------------------------------------------------------------------------------------------------------------------------
YUJA North........................  Low.......................  Moderate +...........  Moderate to High +...  Low to Moderate.....  Low.
YUJA Central......................  Low.......................  Low..................  Moderate to High.....  Low to Moderate.....  Low.
YUJA East.........................  Low.......................  Low..................  Low..................  Low to Moderate.....  Low.
YUJA Summary......................  Low.......................  Low to Moderate......  Moderate.............  Low to Moderate.....  Low.
Overall Magnitude of Threat.......  Low.......................  Low to Moderate......  Moderate.............  Low to Moderate.....  Low.
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Level of threat: low refers to impacts to the individuals; moderate refers to impacts affecting portions of an analysis unit; high refers to impacts
  that may result in population level effects to the analysis unit.
+ Indicates those analysis units where the magnitude of the threat is the greatest.

Conservation Measures and Existing Regulatory Mechanisms

    Threats may be ameliorated or reduced through the implementation of 
existing regulatory mechanisms or other conservation measures that 
benefit Joshua trees and their habitat. Federal agencies, State 
agencies, and several local communities have adopted and implemented 
laws, regulations, or ordinances and conservation measures that protect 
native habitat and plants such as Joshua trees. Conservation measures 
that assist in reducing or ameliorating individual threats are 
discussed at the end of each of the discussions of individual threats 
in this document and in the SSA report (Service 2023, appendix B, pp. 
152-161).
    For the Joshua trees, a high percentage of occupied habitat 
includes lands conserved as open space and resource lands owned by the 
Federal government, State agencies, and nonprofit organizations, 
including lands covered by conservation easements, which provide a high 
level of protection for the species and their habitat. Conservation is 
categorized by the protected area database (USGS 2018, unpaginated) and 
is based on how the lands are managed. Approximately 3 million ac (1.2 
million ha; 32 percent) of habitat occupied by the Joshua trees is 
fully conserved, including 23 percent of Yucca brevifolia's and 41 
percent Y. jaegeriana's distribution. Considering lands that are 
protected with allowable low-intensity or isolated impacts (e.g., OHV 
use), the percentage increases to 75 percent, including 59 percent of 
the range of Y. brevifolia and 89 percent of the range of Y. 
jaegeriana. Additionally, approximately 82 percent of the land within 
the distribution of Joshua trees is federally owned by the Service, 
BLM, National Park Service (NPS), U.S. Forest Service (USFS), and 
Department of Defense (DoD) (see tables 4-1 and 6-5 in the SSA report 
(Service 2023, pp. 33, 87)).
    Federal lands are less likely to be developed and each agency 
follows established regulations and policies that provide for the 
consideration or management of Joshua trees or their habitat, including 
the following Federal regulations and policies: NEPA, Federal Land 
Policy and Management Act of 1976 (43 U.S.C. 1701 et seq.), National 
Forest Management Act (16 U.S.C. 1600 et seq.), Sikes Act and Sikes Act 
Improvement Act of 1997 (16 U.S.C. 670 et seq.), National Park Service 
Organic Act of 1916 (54 U.S.C. 100101 et seq.), Organic Administration 
Act of 1897 (16 U.S.C. 475, 477-478, 479-481, and 551) and the 
Multiple-Use, Sustained-Yield Act of 1960 (16 U.S.C. 528 et seq.), 
Wilderness Act (16 U.S.C. 1131 et seq.), Endangered Species Act (i.e., 
protections for other listed species may benefit the Joshua tree or its 
habitat), California Desert Protection Act (43 U.S.C. 1781 and 1781a), 
and the Desert Renewable Energy Conservation Plan.
    Joshua trees are currently addressed under the California 
Environmental Quality Act and several local jurisdictions in California 
have enacted specific tree ordinances for the Joshua trees. The Clean 
Air Act and California climate policies that help to mitigate climate 
change may also contribute to improved habitat conditions for Joshua 
trees in the future (see appendix B of the

[[Page 14550]]

SSA report (Service 2023, pp. 152-161)). Though Joshua trees are not 
listed under the California Endangered Species Act (CESA), Yucca 
brevifolia has been considered a candidate for listing since 2020 (CDFW 
2022, p. 1). As a candidate for listing under CESA, Y. brevifolia is 
temporarily afforded the same protections as a State-listed endangered 
or threatened species. The California Department of Fish and Wildlife 
(CDFW) has since completed their Status review of the Y. brevifolia and 
recommended that listing Y. brevifolia was not warranted (CDFW 2022, 
entire); the issue is now with the California Fish and Game Commission 
for a final decision. The Commission plans to make a final decision on 
whether to list the western Joshua tree under CESA in February 2023, to 
allow for additional Tribal consultation and deliberation time 
(CALSPAN, 2022). If the Commission accepts CDFW's recommendation, the 
Y. brevifolia would no longer be a candidate for listing under CESA.
    The States of Arizona, Nevada, and Utah have no special designation 
or protection for Joshua trees as a state listed species, however there 
are regulations in place that limit collection of native desert plants. 
In Arizona, Joshua trees are a salvage restricted native plant, as 
prescribed in title 3, chapter 7, of the Arizona Revised Statutes at 
section 3-903B.2., which means that a permit is required for removal/
collection (Arizona Department of Agriculture, 2016). Similarly, Joshua 
trees, and all members of the Yucca genus, are protected in the State 
of Nevada from commercial collection (see title 47, chapter 527, of the 
Nevada Revised Statutes, at section 527.060 et seq.); commercial 
removal and sale of Yucca harvested from State, county, or privately 
owned land requires a permit from the Nevada State Forester Firewarden.

Cumulative and Synergistic Effects

    We note that, by using the SSA framework to guide our analysis of 
the scientific information reviewed and documented in the SSA report, 
we have not only analyzed individual effects on the species, but we 
have also analyzed their potential cumulative effects. We incorporate 
the cumulative effects into our SSA analysis when we characterize the 
current and future conditions of the species. To assess the current and 
future condition of the species, we undertake an iterative analysis 
that encompasses and incorporates the threats individually and then 
accumulates and evaluates the effects of all the relevant factors that 
may be influencing the species, including threats and conservation 
efforts. Because the SSA framework considers not just the presence of 
the factors, but to what degree they collectively influence risk to the 
entire species, our assessment integrates the cumulative effects of the 
factors and replaces a standalone cumulative effects analysis.
    The threats acting on a species or its habitat do not typically 
operate in isolation but could impact the species or its habitat in 
conjunction with other threats. Individually identified threats may not 
rise to a level of concern or be insignificant in nature and not 
influence a decline in the species' status on the landscape. However, 
combined, these threats may result in a greater overall cumulative 
impact to a species or its habitat. In some cases, threats may also act 
synergistically, with the resulting impact being greater than if the 
threats were merely combined. These cumulative or synergistic impacts 
could result in an increased reduction in individual and habitat 
resource needs that may result in a loss of resiliency for a species. 
For example, the severity of drought events could increase under future 
climate conditions, which would further dry and stress vegetation and 
potentially make vegetation more vulnerable to wildfire, and predation. 
In our analysis of the threats facing Yucca brevifolia and Y. 
jaegeriana, we took the potential cumulative or synergistic effects of 
threats into consideration, and they are part of our discussion and 
conclusions regarding each threat currently and into the future.
Current and Future Condition
    To evaluate the biological status of Yucca brevifolia and Y. 
jaegeriana both currently and into the future, we assess a range of 
conditions to allow us to consider the species' resiliency, redundancy, 
and representation. We evaluate how anthropogenic threats such as 
habitat loss and degradation, invasive grasses, increased risk of 
wildfire, climate change, and predation influence the resiliency, 
redundancy, and representation of Joshua trees in regional analysis 
units to describe the species' future viability. The viability of Y. 
brevifolia and Y. jaegeriana depends on maintaining multiple 
populations with sufficient redundancy and resiliency over time across 
each species' distribution.

Current Condition

    We assess the Joshua trees' current condition by evaluating 
resiliency, representation, and redundancy. To assess current 
conditions for Yucca brevifolia and Y. jaegeriana, each species' range 
was divided into analysis units that are representative of the range of 
biotic and abiotic features of Joshua trees' habitat. A high overall 
resiliency condition score means all population needs are clearly met 
and that the species in that unit is sufficiently resilient to 
environmental variation in the range experienced by the species in the 
recent past; a highly resilient analysis unit is unlikely to become in 
danger of extinction and is more likely to contribute to species 
viability. A medium overall resiliency condition score means some 
habitat or demographic needs are minimally present while others may be 
met in the analysis unit, but we project that the analysis unit likely 
has the resiliency necessary to recover from stochastic variability. 
For units with a medium overall resiliency condition score, although 
occupancy may be lost in some areas, these units are unlikely to become 
in danger of extinction, and the functionality of the unit is likely to 
be retained and contribute to species viability. An overall low 
population resiliency condition score means that one or more habitat or 
demographic needs were not met, or all needs are at such low condition 
that there is a higher probability that the analysis unit may be in 
danger of extinction; a low resiliency analysis unit is unlikely to 
contribute substantially to species viability.
Current Resiliency, Redundancy, and Representation
    Resiliency is the ability of populations to respond to stochastic 
variation despite the current level of threat. Based on the habitat and 
demographic needs identified in the SSA report, condition categories 
were defined where there was sufficient information to describe low, 
moderate, and high condition (see table 7-2 in the SSA report (Service 
2023, p. 92)). We identified four condition categories including 
habitat quantity (availability of occupied habitat), habitat quality 
(invasive grass cover), and two demographic parameters (tree density 
and recruitment). The analysis units were then assessed to evaluate 
population resiliency based on these categories (see table 7-3 in the 
SSA report (Service 2023, p. 93)). Chapter 7 of the SSA report 
describes the parameters and assessment methodology (Service 2023, pp. 
87-100).
    We evaluated the Joshua trees' redundancy and representation in the 
context of the species' needs (see chapters 5 and 7 of the SSA report 
for a description of the assessment methodology (Service 2023, pp. 41-
50,

[[Page 14551]]

87-100)). Redundancy describes the ability of a species to withstand 
catastrophic events that would result in the loss of a substantial 
component of the species' total overall population and can be assessed 
based on the number of populations and their resiliency, distribution, 
and connectivity. Representation is the ability of a species to 
withstand and adapt to long-term changes in environmental conditions 
(i.e., significant changes outside the range of normal year-to-year 
variations). It is measured by the breadth of genetic or ecological 
diversity within and among populations and is used to evaluate the 
probability that a species can adapt to environmental changes.
I. Yucca brevifolia
    Resiliency: Yucca brevifolia occupies a large and diverse area of 
4.4 million ac (1.8 million ha) in two analysis units of similar size 
within the western Mojave Desert. We consider both YUBR North and YUBR 
South highly resilient due to moderate to high condition for both 
habitat (e.g., quantity and quality) and demographic (e.g., tree 
density and recruitment) parameters (see table 7-3 in the SSA report 
(Service 2023, p. 93)). The range of Y. brevifolia is comprised of 
approximately 3.3 million ac (1.3 million ha: 74 percent) of Federal 
lands that are administered by the NPS, BLM, USFS, and Department of 
Energy, as well as military lands. The species' distribution also 
includes several National Parks (Joshua Tree National Park, Death 
Valley National Park), California State Parks (Red Rock Canyon State 
Park), and County parks and preserves where Joshua trees are protected 
and managed. The southern analysis unit (YUBR South) has a higher 
proportion of the area privately owned (45.6 percent) and potentially 
subject to development, but half (52 percent) of the unit is under 
Federal management. The species' distribution in this unit occurs along 
a latitudinal gradient, and the southern analysis unit is currently, 
and likely historically, more drought-stressed and has a higher 
magnitude of threat associated with drought-exacerbated predation and 
herbivory. There is recent site-specific evidence of reduced survival, 
recruitment, and the availability of recruitment habitat at lower 
elevations in YUBR South. However, the available data is limited both 
spatially and temporally and cannot be evaluated in a historical 
context; therefore, it is not clear if these data points from a 12-year 
period represent natural variability or are an early indication of the 
potential effects of increased temperatures and prolonged drought. We 
also lack data and information on population trend and recruitment for 
the rest of the species' ranges; therefore, these trends were not 
extrapolated rangewide. Based on the best available data the current 
demographic condition for YUBR South is moderate to high. In contrast, 
YUBR North is characterized by lower temperatures and higher 
precipitation, which contribute to higher recruitment condition and 
moderate to high demography overall. Although there is site-specific 
evidence that demographic and habitat conditions may have declined in 
recent years, these changes have not been to the level that puts Joshua 
trees at risk; we consider that both populations currently have a high 
capacity to withstand or recover from stochastic variability due to the 
large distribution, moderate to high demography, and large percentage 
of the distribution conserved or managed on Federal lands. Yucca 
brevifolia's resiliency is moderate-high to high throughout its range 
and for all condition categories (habitat quantity, habitat quality, 
tree density, and recruitment), and overall high for YUBR North and 
YUBR South (see table 7-3 in the SSA report (Service 2023, p. 93)).
    Redundancy: We consider Yucca brevifolia to have sufficient 
redundancy to withstand catastrophic events. YUBR South and YUBR North 
are spread across a very large area of mostly intact habitat that 
supports resource needs and contributes to a high level of redundancy. 
No range contraction has occurred over the last 30 to 40 years, based 
on distribution mapping (Rowlands 1978, p. 52; Esque 2022a, pers. 
comm.). The large amount of occupied habitat indicates that the range 
is occupied by millions of Joshua trees distributed across a 
latitudinal gradient of approximately 300 miles (mi) (483 kilometers 
(km)).
    Additionally, the majority of occupied habitat is located on 
Federal lands--with some degree of regulatory protection, management, 
and reduced probability of anthropogenic disturbance--and is less 
likely to be impacted by anthropogenic development. For example, NPS 
prohibits removal of Joshua trees in National Parks, actively monitors 
the species, and conducts habitat restoration for the species. The risk 
of catastrophic loss is very low because the species is spread across a 
4.4-million-ac (1.8-million-ha) area. Across the range of Y. 
brevifolia, approximately 80 percent of the occupied habitat is 
characterized by a natural fire regime (i.e., fire return interval of 
greater than 100 years), and greater than 50 percent of the species' 
range is characterized as no or low risk from invasive grasses. 
Although there is recent evidence of reduced recruitment and survival 
under extreme drought conditions, these effects are documented on a 
limited to relatively small area of the range; thus, we do not 
anticipate that current redundancy is substantially reduced such that 
wildfire, prolonged drought, or extreme predation and herbivory places 
either analysis unit in danger of extinction.
    Representation: We evaluated representation in Yucca brevifolia 
based on the ecological diversity of the habitats it occupies, as a 
surrogate for genetic diversity, and the species' life-history 
characteristics that support or hinder adaptive capacity (see appendix 
A in the SSA report (Service 2023, p. 150). Adaptive capacity was 
evaluated following Thurman et al. 2020 (entire) to characterize Y. 
brevifolia's ability to persist in place or shift in space in response 
to changes in its environment. Representation, as measured by the 
ecological diversity of habitats, is high for Y. brevifolia, as the two 
analysis units occupy highly diverse areas within the Mojave and Great 
Basin Deserts that include differences in elevation, aspect, soil type, 
temperature, rainfall, and vegetation communities. The large area that 
the species occupies, its broad distribution, and its ability as a 
habitat generalist promote higher adaptive capacity. We do not 
anticipate current site-specific reductions in recruitment to 
substantially reduce abundance or representation. Across these 
different environmental gradients, Y. brevifolia exhibits variability 
in growth and reproductive strategies, including increased asexual 
production. The clonal growth strategy increases persistence of the 
individual under stress, such as wildfire (Rowlands 1978, p. 50; 
Harrower and Gilbert 2021, p. 11; Esque 2022a, pers. comm.), which 
along with the Joshua trees' long lifespan, facilitates the ability of 
Y. brevifolia to persist in place in response to long-term or slow 
changes in its environment (Thurman et al. 2020, entire). Conversely, 
Joshua trees' long lifespan, limited reproductive events, long 
generation time, and extended age of sexual maturity limit the ability 
of Y. brevifolia to adapt to short-term changes in its environment. Its 
adaptive capacity and the extent that its populations can persist in 
place in the face of variable environmental conditions may also be 
constrained by its obligate mutualism with the yucca moth; we do not 
have information to assess the adaptive capacity of the yucca moth. 
Lastly, we conclude that the species has limited

[[Page 14552]]

dispersal capabilities based on the average dispersal distances of the 
rodent seed dispersers and through the absence of substantial range 
expansion in the last several thousand years. Therefore, Y. brevifolia 
is unlikely to be able to shift in space beyond average dispersal rates 
in response to changing environmental conditions. However, the species 
has other life-history characteristics that confer representation, 
including high ecological variability and the capacity to persist under 
similar environmental conditions as it has experienced in the past. 
Although there is recent site-specific evidence of reduced recruitment 
and survival under extreme drought conditions, the species currently 
has the capacity to withstand and adapt to changes in environmental 
conditions.
    Viability: Currently, we consider Yucca brevifolia to have adequate 
resiliency, redundancy, and representation throughout its range to 
maintain species viability. The species' current distribution is large 
(approximately 4.4 million ac (1.8 million ha)), occupies a diverse 
region of topographic and ecological diversity, and spans a large 
latitudinal gradient of approximately 300 mi (483 km), which 
collectively confers both redundancy and representation. We consider 
total abundance across the species' range to be high, although tree 
densities vary and recruitment may already be reduced in the southern 
portion of the range. Population resiliency is currently high in the 
YUBR North and YUBR South analysis units based on the current low-to-
moderate level of threat. Drought stress at lower latitudes and 
elevations due to rising temperatures and drought conditions resulting 
in decreased tree vigor, mortality, reduced recruitment, and increased 
herbivory and predation may impact individuals or localized areas but 
are not anticipated to reduce the viability of the species.
II. Yucca jaegeriana
    Resiliency: Yucca jaegeriana is distributed across a 4.9-million-
acre (1.9-million-ha) area in three analysis units across the eastern 
Mojave Desert and a small portion of the southern Great Basin Desert 
and western Sonoran Desert, which we consider in high condition for 
habitat quantity. Approximately 89 percent of Y. jaegeriana's 
distribution occurs on federally owned or managed land; private land 
ownership accounts for only 7 percent of modeled habitat that primarily 
occurs in YUJA East (23.5 percent). Like Y. brevifolia, Y. jaegeriana 
occurs along a latitudinal gradient, and the southernmost analysis unit 
is exposed to more drought stress and has the potential for higher 
drought-exacerbated predation and herbivory, although we have limited 
data on how prevalent this threat is in Y. jaegeriana relative to 
historical conditions. YUJA North has moderate resiliency due to lower 
demographic condition, although the unit has a large quantity of 
occupied habitat. YUJA Central has high population resiliency despite 
lower condition for habitat quality and demographic condition. YUJA 
East has moderate resiliency overall, due to the smaller size of the 
analysis unit and lower tree density and recruitment. Therefore, we 
consider Y. jaegeriana analysis units to have moderate to high 
resiliency and able to withstand environmental stochasticity (see table 
7-3 in the SSA report (Service 2023, p. 93)), due to high habitat 
quality and quantity associated with the large percentage of the 
distribution of conserved or managed habitat on Federal lands.
    Redundancy: We conclude that current redundancy is high in Yucca 
jaegeriana because YUJA Central, YUJA North, and YUJA East analysis 
units occur across a very large area of mostly intact habitat that 
supports resource needs. No range contraction has occurred over the 
last 40 years based on distribution mapping (Rowlands 1978, p. 52; 
Esque 2022a, pers. comm.), though wildfire has impacted trees in 
localized areas in YUJA North and YUJA Central. Additionally, plants 
are located primarily on Federal lands with less probability of 
development. The risk of catastrophic loss is very low because the 
species is spread across a 4.9-million-acre (1.9-million-ha) area 
distributed over a latitudinal gradient of approximately 300 mi (483 
km) and includes potentially millions of individual trees. Despite 
recent evidence of localized wildfire impacts and the invasive grass-
wildfire cycle, we conclude that current redundancy is sufficiently 
high such that wildfire, prolonged drought, or extreme predation and 
herbivory does not place any analysis unit of Y. jaegeriana in danger 
of extinction.
    Representation: We evaluated representation in Yucca jaegeriana 
with respect to ecological diversity and life-history characteristics 
that support or hinder adaptive capacity. Adaptive capacity was 
evaluated following Thurman et al. (2020, entire) to characterize Y. 
jaegeriana's ability to persist in place or shift in space in response 
to changes in its environment. The large area that the species 
occupies, its broad distribution, and its ability as a habitat 
generalist promote higher adaptive capacity. The clonal growth strategy 
increases persistence of the individual under stress, such as wildfire 
(Rowlands 1978, p. 50; Harrower and Gilbert 2021, p. 11; Esque 2022a, 
pers. comm.), which along with the Joshua trees' long lifespan, 
facilitates the ability of Y. jaegeriana to persist in place in 
response to long-term or slow changes in its environment (Thurman et 
al. 2020, entire). Conversely, Joshua trees' long lifespan, limited 
reproductive events, long generation time, and extended age of sexual 
maturity limit the ability of Y. jaegeriana to adapt to short-term 
changes in its environment. Its adaptive capacity and the extent that 
its populations can persist in place in the face of variable 
environmental conditions may also be constrained by its obligate 
mutualism with the yucca moth; we do not have information to assess the 
adaptive capacity of the yucca moth. Lastly, we conclude that the 
species has limited dispersal capabilities based on the average 
dispersal distances of the rodent seed dispersers and through the 
absence of substantial range expansion in the last several thousand 
years. Therefore, Y. jaegeriana is unlikely to be able to shift in 
space beyond average dispersal rates in response to changing 
environmental conditions. The species has other life-history 
characteristics that confer representation, including high ecological 
variability and the capacity to persist under similar environmental 
conditions as it has experienced in the past. However, there is some 
preliminary evidence that Y. jaegeriana's shorter stature and extensive 
branching closer to the ground may make it more susceptible to wildfire 
than Y. brevifolia (Cornett 2022, pp. 186-188). Ecological diversity is 
high, as Y. jaegeriana occupies an extensive area covering 
approximately 300 mi (483 km) from north to south and there is a high 
degree of variability in abiotic and biotic conditions within these 
habitats. YUJA North has high ecological diversity, as this unit is 
topographically diverse with areas of low, medium, and high elevation. 
Ecological variability is moderate to high both in topographic 
heterogeneity and the number of ecoregions. Therefore, we consider Y. 
jaegeriana to have sufficient representation to adapt to environmental 
conditions over time; however, we conclude that Y. jaegeriana has 
limited capacity to shift in space to overcome more rapid or extreme 
variability.
    Viability: Currently, we consider Yucca jaegeriana to have adequate

[[Page 14553]]

resiliency, redundancy, and representation throughout its range to 
maintain species viability. The species' distribution is currently 
large, approximately 4.9 million ac (1.9 million ha), and it occupies a 
diverse region of topographic and ecological diversity that spans a 
large latitudinal gradient of approximately 300 mi (483 km), which 
confers both redundancy and representation. We characterize abundance 
as low to moderate condition across the three analysis units based on 
available tree density information; although tree densities vary and we 
assumed them to be lower in warm environments. Population resiliency is 
currently moderate to high across the three analysis units based on the 
amount and quality of habitat available, and the current low to 
moderate levels of threat. Although drought stress at lower latitudes 
and elevations due to rising temperatures and drought conditions may be 
impacting individuals or localized areas; we conclude that overall, 
they do not reduce the viability of the species. Thus, the species has 
sufficient viability to withstand the current level of threats.

Future Condition

    In this section, we summarized the Joshua trees' future condition 
to 2069 where we can reliably forecast threats and the species' 
response to those threats. Over the next 47 years (approximately one 
generation and when trees can reproduce sexually), we can reliably 
characterize Joshua trees' viability where our confidence is greatest 
with respect to the range of projected plausible threats and the 
species' response. There are key areas of uncertainty, primarily 
regarding the two species' responses to projected future climate 
conditions, that do not allow us to reliably project the Joshua trees' 
status to end of century, discussed above in Foreseeable Future and 
below in the Finding. This is a shorter timeframe than we evaluated for 
future scenarios in the SSA report. For our evaluation of future 
condition (2040-2069), we rely on the same assumptions and data sources 
about the extent and magnitude of threats projected over time in 
Scenarios I and II of the SSA report for the primary threats--habitat 
loss, invasive grasses, wildfire, and future climate change--
considering the time period from 2040-2069 along the trajectory 
projected for Scenarios I and II. Our evaluation of future condition 
summarized below considered the effects of threats individually and 
cumulatively to both species of Joshua tree.
    In 2040-2069, we project the two species to continue to occupy and 
maintain viability in most of their current ranges, despite forecasted 
temperature increases (Figure 4-1 in Service 2023, p. 31). We project 
adult plant survival and persistence, and clonal growth to continue; 
and the species distribution to remain similar or slightly reduced 
relative to current conditions in unburned habitats across their 
ranges. We project seedling recruitment will continue to occur at 
reduced levels relative to current conditions due to increased drought 
stress in areas modeled to be climatically unfavorable, with the 
greatest reduction projected at lower elevations and latitudes. In low 
and moderate severity burned habitats, we project recovery of the two 
species in habitats that do not have an invasive grass-wildfire cycle, 
though recovery times may take longer due to projected drought 
conditions. We project localized losses of Joshua trees in developed 
areas and in areas with an invasive grass-wildfire cycle. We forecast 
the conditions for 2040-2069 to be similar to current conditions but 
with slight reductions in resiliency from declines in recruitment, tree 
density and possibly occupied habitat.
I. Yucca brevifolia
    Resiliency: Based on its long persistence across large areas with 
varied environmental conditions, we project that Yucca brevifolia will 
continue to occupy a large and diverse area of approximately 4 million 
ac (1.6 million ha) in two analysis units of similar size within the 
western Mojave Desert. We project the species' distribution will 
continue to occur along a latitudinal gradient, similar to its current 
distribution. We project the condition of the habitat and demographic 
parameters to be slightly reduced in more arid areas, including at low 
elevations within the analysis unit and at lower latitude (YUBR South), 
with potential localized areas of habitat loss. We consider both YUBR 
North and YUBR South to be highly resilient, due to moderate to high 
condition for habitat (e.g., quantity and quality) and demographic 
(e.g., tree density and recruitment) parameters, and accounting for the 
potential for localized reductions in recruitment and survival in YUBR 
South. This species will continue to occupy habitat primarily in 
Federal ownership and we project current management protections 
afforded to the species will continue. The southern analysis unit (YUBR 
South) has a higher proportion of privately owned land (45.6 percent) 
and we project approximately 11 percent of the analysis unit may be 
lost to development in low elevation areas projected to have reduced 
recruitment. However, approximately 50 percent of the unit is under 
Federal management and most of that area is likely to continue to 
support the species in 2040-2069. YUBR South will continue to 
experience more drought-stress with localized areas of reduced 
recruitment and tree mortality, with a higher magnitude of threat 
associated with drought-exacerbated predation and herbivory. Based on 
our projections, the future demographic condition for YUBR South is 
moderate and reduced from current conditions; and the analysis unit is 
forecasted to maintain high resiliency in the foreseeable future. YUBR 
North will continue to experience lower temperatures and higher 
precipitation than YUBR South which contributes to higher recruitment 
condition and high demography as well as high population resiliency.
    Overall, our analysis indicated that occupancy will be maintained 
throughout the range of Yucca brevifolia, and approximately 90 percent 
of the current distribution will be viable in the foreseeable future 
(2040-2069). We project that high resiliency for Y. brevifolia will 
continue to be maintained in both analysis units; and will be similar 
or slightly reduced relative to current conditions because tree 
densities may be lower, and recruitment reduced. We project that these 
changes in resiliency will not put the Y. brevifolia in danger of 
extinction, as both analysis units are likely to be able to withstand 
stochastic events and contribute to species viability.
    Redundancy: We consider future redundancy in Yucca brevifolia to be 
high and similar to current redundancy. YUBR South and YUBR North will 
continue to occupy a very large area of mostly intact habitat that 
supports the species' resource needs. We project small, localized areas 
of habitat loss will occur (approximately 10 percent of the current 
range) and that 90 percent of the range will maintain viability by 
2040-2069. The large amount of occupied habitat indicates that the 
range is occupied by millions of Joshua trees distributed across a 
latitudinal gradient of approximately 300 miles (mi) (483 kilometers 
(km)).
    Additionally, the majority of occupied habitat will be located on 
Federal lands--with some degree of regulatory protection, management, 
and reduced probability of anthropogenic disturbance--and is less 
likely to be impacted by anthropogenic development. The risk of 
catastrophic

[[Page 14554]]

loss is very low because the species is spread across an approximately 
4-million-ac (1.6-million-ha) area. Across the range of Y. brevifolia, 
we project approximately 80 percent of the occupied habitat is 
characterized by a natural fire regime (i.e., fire return interval of 
greater than 100 years), and approximately 80 percent of the species' 
range is characterized as no or low risk from invasive grasses. 
Although we project reduced tree density and recruitment under extreme 
drought conditions, both analysis units are forecasted to be highly 
resilient. Therefore, we anticipate that future redundancy will be 
sufficient to withstand catastrophic events associated with threats 
(e.g., wildfire, prolonged drought, or extreme predation and 
herbivory).
    Representation: Representation, as measured by the ecological 
diversity of habitats, remains high and we project it to be similar or 
slightly reduced from current condition, as we project the two analysis 
units to occupy highly diverse areas within the Mojave and Great Basin 
Deserts that include differences in elevation, aspect, soil type, 
temperature, rainfall, and vegetation communities. The large area that 
the species occupies, its broad distribution, and its ability as a 
habitat generalist promote higher adaptive capacity. We do not 
anticipate projected reductions in tree density and recruitment to 
substantially reduce abundance or representation. Across these 
different environmental gradients, Y. brevifolia will continue to 
exhibit variability in growth and reproductive strategies, including 
the potential for increased asexual production to support persistence 
of individuals under stress. Its adaptive capacity and the extent that 
its populations can persist in place in the face of variable 
environmental conditions may also be constrained by its obligate 
mutualism with the yucca moth; but we were not able to reliably project 
changes to this mutualism. Lastly, we project that the species' 
dispersal capabilities will remain limited and similar to current 
conditions. Although we project reduced tree density and recruitment, 
we forecast the species to retain the capacity to withstand and adapt 
to changes in environmental conditions.
    Viability: Our analysis indicates that approximately 90 percent of 
the current distribution will be viable in the foreseeable future 
(2040-2069), though tree densities may be lower and recruitment 
reduced. We predict that resiliency, redundancy, and representation for 
Yucca brevifolia would continue to be viable and similar or slightly 
reduced relative to current conditions. All analysis units will be 
occupied, and the distribution includes a large and diverse area of 
mostly intact habitat that supports resource needs and the ability to 
withstand stochastic variability in environmental conditions. We 
project the species to have sufficient population resiliency and the 
ability to respond to stochastic and year-to-year variability. Because 
Y. brevifolia is long-lived, occupies a broad distribution, is a 
habitat generalist, is capable of asexual reproduction, and occupies 
numerous ecological settings, we project that the species has 
sufficient adaptive capacity and representation to adapt to changing 
environmental conditions. Therefore, future events, such as severe 
wildfire due to invasive grasses, or the effects of predation and 
moisture deficit due to long-term drought and increased temperatures 
due to climate changes would not lead to population- or species-level 
declines that would limit species viability.
    Under the range of threats forecasted, we project that Yucca 
brevifolia will maintain high population resiliency. We project 
redundancy to be similar to the current condition with a similar 
distribution and similar population size. Our analysis indicates that 
at least 90 percent (4 million ac (1.6 million ha)) of the current 
distribution will be occupied. We consider this acreage and the 
species' broad distribution to confer sufficient redundancy for the 
species to withstand large-scale wildfires, prolonged drought, and 
episodes of severe predation. No analysis unit is forecasted to be in 
danger of extinction under a catastrophic event. Similarly, we project 
representation to be similar or slightly reduced compared to current 
conditions and that Y. brevifolia will retain adequate representation, 
despite the increased risk of wildfires, increased temperatures, and 
potential for prolonged drought. We considered the possibility of 
potential habitat expansion in the future, but we project that it will 
be limited by dispersal distance and the general lack of continuity 
between currently occupied habitat and habitat forecasted to be 
climatically favorable in the future. Therefore, we did not include 
potential habitat expansion in our projections for resiliency, 
redundancy, or representation. We project that future resiliency, 
redundancy, and representation contribute to a viability that does not 
place Y. brevifolia in danger of extinction.
II. Yucca jaegeriana
    Resiliency: Based on its long persistence across large areas with 
varied environmental conditions, we project that Yucca jaegeriana will 
continue to occupy a large and diverse area of approximately 4.4 
million ac (1.8 million ha) in three analysis units of similar size 
within the eastern Mojave Desert, the southern Great Basin Desert, and 
western Sonoran Desert. We project that the species' distribution in 
the future will be similar to its current distribution along a 
latitudinal gradient. We consider all three units, YUJA North, YUJA 
Central, and YUJA East to be moderately resilient due to moderate to 
high condition for habitat parameters (e.g., quantity and quality), 
despite low to moderate demographic (e.g., tree density and 
recruitment) condition projected due to the forecasted increases in 
drought stress and reduced recruitment. We project the condition of the 
habitat and demographic parameters to be slightly reduced in more arid 
areas, including at low elevations and in the analysis unit at lower 
latitude (YUJA East), with localized areas of habitat loss. We forecast 
greater potential for negative impacts to YUJA East due to the 
increasing temperatures and drought affecting habitat quantity, habitat 
quality, and demographic parameters due to its lower latitude and 
elevation. YUJA North and YUJA Central have higher but still moderate 
resiliency because they occur at higher latitudes, but portions of 
these analysis units also occur at lower elevation and are subject to 
the increased aridity and greater effects from climate change. In 
addition, these analysis units (YUJA North and YUJA Central) in the 
northern portion of the range have burned, have higher invasive grass 
cover, and are at increased risk of wildfire in the future with 
potential impacts to both habitat and demographic parameters. This 
species will continue to occupy habitat primarily in Federal ownership 
and we project current management protections afforded to the species 
will continue.
    Overall, our analysis indicated that occupancy will be maintained 
throughout the range of Yucca jaegeriana and approximately 90 percent 
of the current distribution will be viable in the foreseeable future 
(2040-2069). We project moderate resiliency for Y. jaegeriana in all 
three analysis units that will be similar or slightly reduced relative 
to current conditions because tree densities may be lower and 
recruitment reduced. These changes in resiliency are not projected to 
put Y. jaegeriana at risk of extinction, as all three analysis units 
are likely to be able to withstand stochastic events and contribute to 
species viability.
    Redundancy: Future redundancy will remain high for Yucca jaegeriana 
and

[[Page 14555]]

similar or slightly reduced relative to current redundancy. YUJA 
Central, YUJA North, and YUJA East analysis units will continue to be 
occupied and viable across a very large area of mostly intact habitat 
that supports the species' resource needs. Additionally, plants are 
located primarily on Federal lands with less probability of 
development. The risk of catastrophic loss is very low because we 
project the species to occur across an approximately 4.4-million-acre 
(1.8-million-ha) area distributed over a latitudinal gradient of 
approximately 300 mi (483 km) and include potentially millions of 
individual trees. Despite projected wildfire impacts and the invasive 
grass-wildfire cycle, we conclude that future redundancy is 
sufficiently high to withstand catastrophic events associated with 
wildfire, prolonged drought, or extreme predation and herbivory.
    Representation: Representation, as measured by the ecological 
diversity of habitats, remains high and slightly reduced from current 
condition, as we project the three analysis units to occupy highly 
diverse areas within the Mojave, Great Basin, and Sonoran Deserts that 
include differences in elevation, aspect, soil type, temperature, 
rainfall, and vegetation communities. The large area that the species 
occupies, its broad distribution, and the fact that it is a habitat 
generalist promotes higher adaptive capacity. We do not anticipate 
reductions in tree density and recruitment to substantially reduce 
abundance or representation. Across these different environmental 
gradients, Yucca jaegeriana will continue to exhibit variability in 
growth and reproductive strategies, including increased asexual 
production to support persistence of the individual under stress. Its 
adaptive capacity and the extent that its populations can persist in 
place in the face of variable environmental conditions may also be 
constrained by its obligate mutualism with the yucca moth; but we were 
not able to reliably project changes to this mutualism. Lastly, we 
project that the species' dispersal capabilities will remain limited 
and similar to the current condition. Although we project reduced tree 
density and recruitment, we project the species to retain the capacity 
to withstand and adapt to changes in environmental conditions.
    Viability: Our analysis indicates that approximately 90 percent of 
the current distribution will be viable in the foreseeable future 
(2040-2069), though densities of plants on the landscape may be lower 
and recruitment reduced at lower latitudes and elevations. We predict 
that resiliency, redundancy, and representation for Yucca jaegeriana 
will continue to be maintained and will be similar or slightly reduced 
relative to current conditions. All analysis units will be occupied, 
and the distribution will include a large and diverse area of mostly 
intact habitat that supports resource needs and the ability to 
withstand stochastic variability in environmental conditions and 
catastrophic events. Because Y. jaegeriana is long-lived, occupies a 
broad distribution, is a habitat generalist, is capable of asexual 
reproduction, and occupies numerous ecological settings, we project 
that the species has sufficient adaptive capacity and representation to 
adapt to changing environmental conditions. Therefore, future events, 
such as severe wildfire due to nonnative grasses, or the effects of 
predation and moisture deficit due to long-term drought and increased 
temperatures due to climate changes in 2040-2069, would not lead to 
population- or species-level declines that would limit species 
viability.
    Under the range of threats forecasted, we project that Yucca 
jaegeriana will maintain moderate population resiliency across its 
range. Redundancy is projected to be similar to or slightly reduced 
relative to current condition with a similar distribution and 
population size considering the potential for decreases in distribution 
and population size as a result of forecasted localized loss of 
occupied habitat in developed areas and at lower elevations and 
latitudes. Our analysis indicates that approximately 90 percent (4.4 
million ac; 1.8 million ha) of the current distribution will be 
occupied and viable. We consider this acreage and the species' broad 
distribution to confer sufficient redundancy for the species to 
withstand potential large-scale wildfires, prolonged drought, and 
episodes of severe predation. No analysis unit is projected to be in 
danger of extinction due to a stochastic or catastrophic event. We 
project representation to be sufficient and slightly reduced relative 
to current conditions, despite the increased risk of wildfires, 
increased temperatures, and potential for prolonged drought. We 
considered the possibility of potential habitat expansion in the 
future; but project that habitat expansion will be limited by dispersal 
capability and the general lack of continuity between currently 
occupied habitat and habitat forecasted to be climatically favorable in 
the future. Therefore, we did not include potential habitat expansion 
in our projections for resiliency, redundancy, or representation. We 
project that future resiliency, redundancy, and representation will 
continue to contribute to viability that does not place Y. jaegeriana 
in danger of extinction.

Overall Synthesis of Future Viability

    Our analyses of the threats in the future support reasonably 
reliable projections of the future status of Yucca brevifolia and Y. 
jaegeriana from 2040-2069. Population resiliency for both species will 
be similar or slightly reduced relative to current conditions, ranging 
from moderate to high. Although there is the potential for localized 
habitat loss, the majority of the range of both species will continue 
to be occupied and viable, including approximately 4 million ac (1.6 
million ha) for Y. brevifolia and 4.4 million ac (1.8 million ha) for 
Y. jaegeriana. All species needs are projected to be met throughout the 
majority of the occupied habitat, including reproduction through 
masting events and asexual/clonal reproduction, although recruitment 
may be lower in some areas. Future resiliency is similar or slightly 
reduced relative to current conditions and we project both species will 
have the ability to withstand environmental stochasticity. Localized 
habitat loss and reductions in recruitment are not projected to 
substantially decrease redundancy and representation. Therefore, both 
species are projected to have the ability to adapt to changes in 
environmental conditions and be able to withstand catastrophic events.

Finding

    Section 4 of the Act (16 U.S.C. 1533) and its implementing 
regulations (50 CFR part 424) set forth the procedures for determining 
whether a species meets the definition of an endangered species or a 
threatened species. The Act defines an ``endangered species'' as a 
species that is in danger of extinction throughout all or a significant 
portion of its range, and a ``threatened species'' as a species that is 
likely to become an endangered species within the foreseeable future 
throughout all or a significant portion of its range. The Act requires 
that we determine whether a species meets the definition of an 
endangered species or a threatened species because of any of the 
following factors:
    (A) The present or threatened destruction, modification, or 
curtailment of its habitat or range;
    (B) Overutilization for commercial, recreational, scientific, or 
educational purposes;
    (C) Disease or predation;

[[Page 14556]]

    (D) The inadequacy of existing regulatory mechanisms; or
    (E) Other natural or manmade factors affecting its continued 
existence.

Status Throughout All of Their Ranges

    After evaluating threats to both of the species and assessing the 
cumulative effect of the threats under the Act's section 4(a)(1) 
factors, we found that while there are threats that are currently 
acting on Yucca brevifolia and Y. jaegeriana such as habitat loss and 
degradation (from urbanization, military training, renewable energy, 
grazing, and OHV use) (Factor A), increased risk of wildfire (Factor 
A), seed predation and herbivory (Factor C), invasive grasses (Factor 
A), and changing climatic trends (e.g., increased temperatures and 
longer more frequent drought periods) (Factor A), including cumulative 
effects, we did not find that the threats are currently acting on 
either of the two species at either a population- or species-level 
scale such that the species are in danger of extinction throughout all 
of their range. The two species are occupying most of their historical 
ranges--which currently extends to over 4.4 million ac (1.8 million ha) 
for Y. brevifolia and 4.9 million ac (1.9 million ha) for Y. 
jaegeriana, as well as a hybrid zone of approximately 121,147 ac 
(49,048 ha). We also considered the inadequacy of existing regulatory 
mechanisms (Factor D) to address the primary threats to Joshua trees 
from the other four factors (Factors A, B, C, and E). We found no 
information to indicate that existing regulatory mechanisms (Factor D) 
in combination with other threats are not helping to address the 
effects of the threats to the species or would negatively affect the 
status of the species. Furthermore, as discussed above, we found 
various Federal and State regulatory mechanisms do currently exist that 
do provide some level of protection for Joshua trees and their habitat.
    Current population resiliency is high for Yucca brevifolia due to 
the large amounts of moderate- to high-quality habitat occupied by the 
species, as well as moderate to high tree density and recruitment 
observed throughout the range. The high level of population resiliency 
indicates that habitat and demographic resource needs are not limiting, 
and the species is currently able to withstand stochastic events. 
Similarly, current population resiliency ranges from moderate to high 
for Y. jaegeriana. Although there is also a large amount of habitat 
occupied by the species, the quality of habitat, tree density, and 
recruitment are reduced due in part to recent wildfires and higher 
levels of invasive grass cover within burned habitat, particularly in 
the northern portion of its range. However, all analysis units of Y. 
brevifolia and Y. jaegeriana currently retain resiliency sufficient to 
withstand stochastic variability because of the quantity of moderate- 
to high-condition habitat occupied by both species.
    While warming and drying climate conditions have been observed, 
there is no evidence to support substantial population size reductions 
and range contraction over the last 40 years based on distribution 
mapping (Rowlands 1978, p. 52; Esque 2022b, pers. comm.). Overall, 
recruitment of both Yucca brevifolia and Y. jaegeriana is currently 
occurring across their respective ranges; although we acknowledge the 
potential for recent, small, and localized declines along the southern 
limit of Y. brevifolia in Joshua Tree National Park, the data does not 
support a population decline. The large area that the two species 
occupy, the broad latitudinal distribution, and the fact that they are 
habitat generalists promote higher adaptive capacity and 
representation. Current reductions in recruitment are not anticipated 
to reduce abundance or representation to the extent of limiting 
viability. Yucca brevifolia and Y. jaegeriana exhibit variability in 
density and reproductive strategies across these different 
environmental gradients, including the relative proportion of asexual 
reproduction. The clonal growth strategy increases persistence of the 
individual under stress (e.g., wildfire), which along with the Joshua 
trees' long lifespan, is anticipated to facilitate the ability of Y. 
brevifolia and Y. jaegeriana to continue to occur in place in response 
to long-term or slow changes in its environment. Additionally, Joshua 
trees are located primarily on Federal lands, which inherently have 
less pressure from anthropogenic development and often provide for 
management of the species. Potential adverse impacts to both species 
are dispersed across their ranges in large, occupied areas that span 
millions of acres across a latitude gradient of approximately 300 mi 
(483 km). This broad distribution and high number of individuals 
occupying the landscape provides redundancy to withstand catastrophic 
events (e.g. wildfire; Factor A) such that these events are not likely 
to place any population of Y. brevifolia or Y. jaegeriana in danger of 
extinction. In addition to the existing regulatory mechanisms already 
in place, several Federal, State, and county agencies have been 
implementing conservation measures through best management practices 
specific to the Joshua trees (Y. brevifolia and Y. jaegeriana), to 
protect and help sustain the species and their habitats where possible. 
The net effect of current and predictable threats to the species, after 
considering applicable conservation measures and existing regulatory 
mechanisms, is not sufficient to cause the species to meet the 
definition of an endangered species. Thus, after assessing the best 
available information, we have determined that Joshua trees (Y. 
brevifolia and Y. jaegeriana) are not currently in danger of extinction 
throughout all of their ranges.
    Therefore, we proceed with determining whether Joshua trees (Yucca 
brevifolia or Y. jaegeriana) are likely to become endangered within the 
foreseeable future throughout their ranges. The two species face a 
variety of future threats, including the threats of habitat loss and 
degradation (from urbanization, military training, renewable energy, 
livestock grazing, and OHV use) (Factor A), increased risk of wildfire 
(Factor A), seed predation and herbivory (Factor C), invasive grasses 
(Factor A), and changing climatic trends, (e.g., increased temperatures 
and longer more frequent drought periods) (Factor A) that have the 
potential to reduce the viability of the two species. Of these threats, 
the primary future threats are the risk of wildfire (Factor A), 
invasive grasses (Factor A), and climate effects (increasing 
temperature, precipitation changes, drought) (Factor A). In the SSA 
report, we evaluated environmental conditions and primary threat 
factors acting on the two species and developed two future scenarios 
projecting to end of century to assist in determining the range of 
potential future conditions.
    We examined the best available data that allow predictions into the 
future which extends as far as those predictions are sufficiently 
reliable to provide a reasonable degree of confidence. Many available 
data sources for the threats evaluated provided specific projections 
out 30 to 50 years. We based our analysis on future projections of 
habitat loss (including renewable energy development, invasive grass 
cover, climate change, and wildfire) and the potential impacts of those 
changes to species needs and habitat conditions. For example, invasive 
grass cover was modeled to 2050 (Comer et al. 2013, Figure 2). Wildfire 
modeling was based on current conditions and is considered accurate for 
the next 30 to 50 years (Klinger 2022, pers. comm.), and development 
and habitat loss projections are available to 2060 (Environmental 
Protection Agency

[[Page 14557]]

2015, entire). The climate change analysis considered bioclimatic 
models that provided projections for 2040-2069 (Thomas et al. 2012, 
entire; Barrows and Murphy-Mariscal 2012, entire).
    Future climate projections for RCP 4.5 and 8.5 and the associated 
species response are more similar at 2050 and begin to diverge after 
2050 based on the different socio-economic and mitigation assumptions 
included in each RCP. Joshua trees' exposure to climatically 
unfavorable conditions and the species' response is also more tractable 
over a shorter time period, which provides greater certainty related to 
threats and the species' responses to those threats, as discussed 
below. We determined the climate projections and the response of Joshua 
trees at the end of century time horizon were too uncertain to rely on 
to analyze future condition. There is a high degree of variability in 
future climate forecasts depending on the global emission scenario 
evaluated at the end of the century and the magnitude of the forecasted 
temperature increase diverge after 2050. There is also a high degree of 
uncertainty in the timing and magnitude of the species' response to 
climatically unfavorable conditions at the end of the century. As a 
result, it is not clear how and when Joshua tree individuals or 
populations may begin to experience the effects of climatically 
unfavorable conditions, including when reduced recruitment may affect 
species viability, how long adult trees may persist in climatically 
unfavorable conditions, and what the physiological thresholds are for 
the species (Thomas 2022, pers. comm; Shafer et al. 2001, p. 207).
    We determined that the best available science regarding the status 
of the species only supports reliable projections to 2040-2069. It was 
noted that beyond 50 years, human decisions that affect global GHG 
emissions are a major source of uncertainty (Terando et al. 2020, pp. 
14-15). Although our SSA report captured the best available information 
on all key influences and the future scenarios provided a range of 
plausible conditions projected to the end of century, we determined 
that using 2040-2069 as the foreseeable future for these listing 
determinations is more appropriate considering the uncertainties 
identified above and our ability to reliably predict threats and the 
species' response.
    In the foreseeable future (2040-2069), we predict that resiliency, 
redundancy, and representation for Yucca brevifolia and Y. jaegeriana 
would continue to be maintained in all analysis units. Because the two 
species are long-lived, occupy broad distributions, are habitat 
generalists, are capable of asexual reproduction, and occupy numerous 
ecological settings, we determined that future stochastic variability 
and catastrophic events, such as severe wildfire due to invasive 
grasses, or the effects of predation and moisture deficit due to long-
term drought and increased temperatures due to climate changes, would 
not lead to population- or species-level declines that would limit 
species viability or persistence. Therefore, in 2040-2069, both species 
are likely to maintain occupancy throughout each analysis unit, within 
a distribution that is similar to or slightly reduced relative to 
current conditions. As a result, each Joshua tree analysis unit is 
likely to contribute representation and redundancy for species 
viability. In addition, most of the habitat occupied by Joshua trees 
occurs on Federal land with existing regulatory mechanisms in place. 
Several Federal, State, and county agencies have been implementing 
conservation measures through BMPs, specific to the Joshua trees (Y. 
brevifolia and Y. jaegeriana), to protect and help sustain the species 
and its habitat where possible and into the future. The net effect of 
predictable future threats to the species, after considering applicable 
conservation measures and the existing regulatory mechanisms, is not 
sufficient to cause the species to meet the definition of a threatened 
species. Thus, after assessing the best available information, we have 
determined that Y. brevifolia and Y. jaegeriana are not likely to 
become endangered within the foreseeable future throughout all of their 
ranges.

Status Throughout a Significant Portion of Its Range

    Under the Act and our implementing regulations, a species may 
warrant listing if it is in danger of extinction or likely to become so 
in the foreseeable future throughout all or a significant portion of 
its range. Having determined that the two species of Joshua tree are 
not in danger of extinction or likely to become so in the foreseeable 
future throughout all of their ranges, we now consider whether they may 
be in danger of extinction or likely to become so in the foreseeable 
future in a significant portion of their ranges--that is, whether there 
is any portion of the species' ranges for which it is true that both 
(1) the portion is significant; and (2) the species is in danger of 
extinction now or likely to become so in the foreseeable future in that 
portion. Depending on the case, it might be more efficient for us to 
address the ``significance'' question or the ``status'' question first. 
We can choose to address either question first. Regardless of which 
question we address first, if we reach a negative answer with respect 
to the first question that we address, we do not need to evaluate the 
other question for that portion of the species' range.
    In undertaking this analysis for Joshua trees, we chose to address 
the status question first. We began by identifying any portions of the 
species' ranges where the biological status of the species may be 
different from its biological status elsewhere in its range. For this 
purpose, we considered information pertaining to the geographic 
distribution of (a) individuals of the species, (b) the threats that 
the species face, and (c) the resiliency condition of populations.
    We evaluated the range of both Joshua tree species to determine if 
either of the species is in danger of extinction now or likely to 
become so in the foreseeable future in any portion of its range. The 
range of a species can be divided into portions in an infinite number 
of ways. We focused our analysis on portions of the species' range that 
may meet the definition of an endangered species or a threatened 
species. For both Joshua tree species, we considered whether the 
threats or their effects on the species are greater in any biologically 
meaningful portion of the species' range than in other portions such 
that the species is in danger of extinction now or likely to become so 
in the foreseeable future in that portion. We examined the following 
threats on both species: habitat loss and degradation (from 
urbanization, military training, renewable energy, grazing, and OHV 
use), invasive grasses, increased risk of wildfire, changing climatic 
trends (e.g., increased temperatures and longer more frequent drought 
periods), and seed predation and herbivory, including cumulative 
effects. As noted above, we defined foreseeable future as 2040-2069, 
the time period for which we can reliably predict the threats and the 
species' response to the threats.
I. Yucca brevifolia
    Yucca brevifolia occupies two distinct areas, which we have 
identified as a northern analysis unit (YUBR North) and a southern 
analysis unit (YUBR South). As discussed in our rangewide analysis, the 
threats of habitat loss and degradation (from urbanization, military 
training, renewable energy, grazing, and OHV use), invasive grasses, 
increased risk of wildfire, changing climatic trends (e.g., increased 
temperatures and longer more frequent drought periods), and seed 
predation and herbivory are known to negatively affect the YUBR North 
and YUBR South analysis units,

[[Page 14558]]

currently and into the future. All these threats are rangewide, meaning 
that they are acting throughout the species' range across all analysis 
units. We identified areas that may have a concentration of threats, 
including threats with the largest potential impacts to the species, 
which may be occurring on a biologically meaningful scale. The 
concentration of threats is more likely to result from increased 
temperatures and drought associated with projected climate change 
(modeled areas of climatically unfavorable habitat), increased risk of 
wildfire, and associated habitat loss in the future. These threats 
occur throughout the YUBR North and YUBR South analysis units to 
varying degrees, but have the highest potential impact to the species 
in the lower elevation habitat areas generally defined as less than 
1,200 m. Therefore, we determined that there may be a geographical 
concentration of threats due to the combination of climate change, risk 
of wildfire, and habitat loss in lower elevation habitat both now and 
in the future.
    Approximately 66 to 88.6 percent of the range of Yucca brevifolia 
is projected to be climatically unfavorable between 2040 and 2069. 
While modeling predicts a large decline in climatically favorable 
habitat, we project that habitat loss will be localized in these 
modeled areas due to uncertainties in the species' response and because 
modeled climatically unfavorable habitat does not equate to an 
immediate loss of occupied habitat or a potential range contraction 
between 2040 and 2069 (Shafer et al. 2001, p. 207). The potential 
species' response is greatest at lower elevation areas that are 
currently experiencing higher levels of drought stress with a projected 
increase in aridity in the foreseeable future. Although there is a low 
probability of natural wildfire ignitions and low frequency of 
wildfires projected for lower elevation areas, habitat recovery post-
fire may be further hindered in these lower elevation zones under 
drought conditions, and human-induced ignitions are projected to be 
higher in YUBR South along the urban-wildland interface. In addition, 
habitat loss due to urbanization and renewable energy development is 
likely to occur in the level terrain that occurs at lower elevation in 
localized areas projected to have reduced recruitment and survival, 
particularly in YUBR South. The effects of these threats on the YUBR 
North and YUBR South analysis units are discussed further above (see 
Threats).
    We next examined the status of the low-elevation areas of the YUBR 
North and YUBR South analysis units, either in total (41 percent of the 
species range) or within each analysis unit (5 and 74 percent 
respectively) by examining the species' response at low elevation and 
the resiliency, redundancy, and representation of Yucca brevifolia in 
these portions. As we evaluate effects to the species in the 
foreseeable future, the cumulative threats at low elevation may result 
in reduced growth and recruitment, with the potential for localized 
tree mortality and thinning across the low-elevation areas. We forecast 
asexual reproduction to be maintained, particularly when trees are 
stressed by drought or in response to wildfire, which supports the 
persistence of the species at low elevations. We project habitat loss 
to be localized, including in a small proportion of the low-elevation 
habitat area. Therefore, Joshua trees are projected to maintain 
viability throughout the majority of the habitat in each analysis unit 
at low elevations into the foreseeable future.
    Population resiliency at low elevations is projected to decrease 
slightly relative to current conditions, including the potential for 
reduced tree densities and recruitment, but is projected to be moderate 
overall because of the large quantity of occupied habitat and moderate 
to high habitat quality. As such, the species will continue to be able 
to withstand stochastic events and normal year-to-year variation in 
environmental conditions within low-elevation areas. In the foreseeable 
future, forecasted tree mortality and localized habitat loss may reduce 
abundance but are not anticipated to result in range contractions or 
cause the species to be more vulnerable to catastrophic events such as 
prolonged drought and wildfire. As a result, redundancy would be 
maintained in low-elevation areas. Similarly, the species' latitudinal 
range is projected to be maintained, and no substantial losses of 
ecological diversity are forecasted at low elevations; therefore, 
representation would be minimally impacted.
    In the foreseeable future, we forecast that the species will 
continue to occupy habitat in lower elevation areas, even in the more 
southern latitudes of Yucca brevifolia's range, where models 
consistently predict a loss of climatically favorable habitat (YUBR 
South). We project that asexual and sexual reproduction will occur 
throughout all analysis units and that ecological diversity will be 
maintained at low elevations. Therefore, resiliency, redundancy, and 
representation for the species would continue to be maintained in the 
lower elevation areas of both analysis units despite the concentration 
of threats in these areas. Overall, the species will continue to 
maintain viability in the foreseeable future within the low-elevation 
areas of each analysis unit, despite the potential for projected 
reductions in demographic measures (tree density and reduced 
recruitment) resulting from all the threats, but particularly from 
changing climatic trends, wildfire, urbanization, and renewable energy 
development threats, which will be more concentrated in the lower 
elevation areas.
    The best scientific and commercial information available indicates 
that in the lower elevations of YUBR North and YUBR South analysis 
units, Yucca brevifolia does not have a different status from its 
rangewide status, so there are no portions of the species' range that 
meet the Act's definition of an endangered species or a threatened 
species. Therefore, we do not need to consider whether any portions are 
significant.
II. Yucca jaegeriana
    Yucca jaegeriana occupies three distinct areas, which we have 
identified as a northern analysis unit (YUJA North), a central analysis 
unit (YUJA Central), and an eastern analysis unit (YUJA East). As 
discussed in our rangewide analyses, the threats of habitat loss and 
degradation (from urbanization, military training, renewable energy, 
grazing, and OHV use), invasive grasses, increased risk of wildfire, 
changing climatic trends (e.g., increased temperatures and longer more 
frequent drought periods), and seed predation and herbivory are known 
to negatively affect the YUJA North, YUJA Central, and YUJA East 
analysis units, currently and into the future. All these threats are 
rangewide, meaning that they are acting throughout the species' range 
across all analysis units. We have identified areas that may have a 
concentration of threats, including threats with the largest potential 
impact to the species, which may be occurring at a biologically 
meaningful scale. This is more likely to result from increased risk of 
invasive grasses and associated wildfire, increased temperatures and 
drought associated with projected climate change in the future (modeled 
areas of climatically unfavorable habitat), and habitat loss from 
urbanization and renewable energy development. These threats occur 
throughout the range to varying degrees but have the highest magnitude 
impact and potential species' response in the lower elevation habitat 
areas (generally defined as less than 1,200 m). Therefore, we 
determined that there may be a geographical concentration of threats

[[Page 14559]]

due to the combination of climate change, risk of wildfire, and habitat 
loss in lower elevation habitat both now and in the future.
    Approximately 66 to 88.6 percent of the range of Yucca jaegeriana 
is projected to be climatically unfavorable in the foreseeable future. 
Although we do not forecast that climatically unfavorable habitat will 
translate to the loss of occupied habitat due to the magnitude of the 
temperature increases forecasted and the timeframe over which the 
species is exposed to climatically unfavorable conditions, the 
potential species' response is greatest in lower elevation areas. Low 
elevation areas are currently experiencing higher levels of drought 
stress with a projected increase in aridity in the foreseeable future. 
There is a higher probability of natural wildfire ignitions in YUJA 
North and YUJA Central due to lightning associated with monsoonal storm 
events. The frequency of wildfires is projected to be higher at lower 
elevation areas, including in portions that have burned recently and 
have higher invasive grass cover. Although fire severity will be lower 
at low elevations, habitat recovery post-fire may be further hindered 
in the future due to drought stress, such as in YUJA East, which occurs 
at both lower elevation and latitude. In addition, habitat loss due to 
urbanization is likely to occur in the level terrain that occurs at 
lower elevation, particularly in YUJA East. Approximately 23.5 percent 
of the analysis unit is under private land ownership (Service 2023, p. 
37), but less than 1 percent of the area of the analysis unit is 
anticipated for further development in the foreseeable future. The 
effects of these threats on the YUJA North, YUJA Central, and YUJA East 
analysis units are discussed further above (see Threats).
    We next examined the status in the low-elevation areas in the YUJA 
North, YUJA Central, and YUJA East analysis units, either in total (60 
percent of the species range) or within each analysis unit (56, 51, and 
98 percent, respectively), by examining the species' response at low 
elevation and the resiliency, redundancy, and representation of Yucca 
jaegeriana in these portions. As we evaluate effects to the species in 
the foreseeable future (2040-2069), the cumulative threats at low 
elevation may result in reduced growth and recruitment, with the 
potential for tree mortality and thinning across the low-elevation 
areas. We forecast asexual reproduction to be maintained, particularly 
when trees are stressed by drought or in response to wildfire, that 
will support the persistence of the species at low elevations. We 
project habitat loss to be localized, including in a small proportion 
of the low-elevation habitat area. Therefore, Joshua trees are 
projected to maintain viability throughout the majority of the habitat 
in each analysis unit at low elevations into the foreseeable future as 
defined.
    Population resiliency at low elevations is projected to decrease 
slightly relative to current conditions, including the potential for 
reduced tree densities and recruitment, but is projected to be moderate 
overall because of the large quantity of occupied habitat and moderate 
habitat quality. As such, the species will continue to be able to 
withstand stochastic events and normal year-to-year variation in 
environmental conditions within the low-elevation areas. In the 
foreseeable future, forecasted tree loss and localized habitat loss may 
reduce abundance; but are not anticipated to result in range 
contractions or cause the species to be more vulnerable to catastrophic 
events such as prolonged drought and wildfire. As a result, redundancy 
would be maintained in the low-elevation areas. Similarly, the species' 
latitudinal range is projected to be maintained in 2040-2069, and no 
substantial losses of ecological diversity or potential arid-adapted 
genotypes are forecasted at low elevations; therefore, representation 
would be minimally impacted.
    In the foreseeable future, we forecast that the species will 
continue to occupy habitat in lower elevation areas, even in the more 
southern latitudes of Yucca jaegeriana's range where models 
consistently predict a decline in climatically favorable habitat (YUJA 
East). We project that asexual and sexual reproduction will occur 
throughout all analysis units and that ecological diversity will be 
maintained at low elevations. Therefore, resiliency, redundancy, and 
representation for the species would continue to be maintained in the 
lower elevation areas of all analysis units despite the concentration 
of threats in these areas. Overall, the species will continue to 
maintain viability in the foreseeable future within the low-elevation 
areas of each analysis unit, despite the potential for projected 
reductions in demographic measures (range thinning and reduced 
recruitment) resulting from all the threats, but particularly from 
changing climatic trends, wildfire, invasive grasses, and urbanization 
threats, which will be more concentrated in the lower elevation areas.
    The best scientific and commercial information available indicates 
that in the lower elevations of the YUJA North, YUJA Central, and YUJA 
East analysis units, Yucca jaegeriana does not have a different status 
from its rangewide status, so there are no portions of the species' 
range that meet the Act's definition of an endangered species or a 
threatened species. Therefore, we do not need to consider whether any 
portions are significant.
    Therefore, we find that Yucca brevifolia and Y. jaegeriana are not 
in danger of extinction now or likely to become so in the foreseeable 
future in any significant portion of their ranges. This does not 
conflict with the courts' holdings in Desert Survivors v. Department of 
the Interior, 321 F. Supp. 3d 1011, 1070-74 (N.D. Cal. 2018), and 
Center for Biological Diversity v. Jewell, 248 F. Supp. 3d 946, 959 (D. 
Ariz. 2017) because, in reaching this conclusion, we did not apply the 
aspects of the Final Policy on Interpretation of the Phrase 
``Significant Portion of Its Range'' in the Endangered Species Act's 
Definitions of ``Endangered Species'' and ``Threatened Species'' (79 FR 
37578; July 1, 2014), including the definition of ``significant'' that 
those court decisions held to be invalid.

Determination of Status

    Our review of the best available scientific and commercial 
information indicates that Yucca brevifolia and Y. jaegeriana do not 
meet the definition of an endangered species or a threatened species in 
accordance with sections 3(6) and 3(20) of the Act. Therefore, we find 
that listing either of the Joshua tree species is not warranted at this 
time. Further discussion of the basis for these findings can be found 
in the Joshua trees' species assessment form, the revised SSA report 
(Service 2023, entire), and other supporting documents (see ADDRESSES, 
above) that capture the scientific information upon which our decision 
was based.

New Information

    We request that you submit any new information concerning the 
taxonomy of, biology of, ecology of, status of, or stressors to Joshua 
trees (Yucca jaegeriana or Y. brevifolia) to the person listed above 
under FOR FURTHER INFORMATION CONTACT, whenever it becomes available. 
New information will help us monitor these species and make appropriate 
decisions about their conservation and status. We encourage local 
agencies and stakeholders to continue cooperative monitoring and 
conservation efforts.

References Cited

    A list of the references cited in this document is available on the 
internet at

[[Page 14560]]

https://www.regulations.gov under Docket No. FWS-R8-ES-2022-0165 in the 
species assessment form, or upon request from the person listed above 
under FOR FURTHER INFORMATION CONTACT.

Authors

    The primary authors of this document are the staff members of the 
Species Assessment Team, Ecological Services Program.

Authority

    The authority for this action is section 4 of the Endangered 
Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).

Martha Williams,
Director, U.S. Fish and Wildlife Service.
[FR Doc. 2023-04680 Filed 3-8-23; 8:45 am]
BILLING CODE 4333-15-P